Deffuant Guillaume

Irstea − Lisc
24, avenue des Landais − B.P. 50085
63172 Aubière Cedex 1 − France
+33 4 73 44 06 14
Contact

Head of LISC and animator of research theme MOTIVE. Social simulation, empathy, machine learning, viability and resilience algorithms.

My research interests are in modelling complex systems (social or ecological dynamics) and assessing their properties such as their viability or resilience. I have a long lasting more personal interest in cognitive sciences and more particularly the concept of empathy. I did my PhD in cognitive sciences (EHESS - Paris VI University) and I got my Habilitation from Clermont University (topic: modelling complex systems). Administrative status: DR1.

From 2007 to 2010, I coordinated the European project PATRES. Currently, I'm involved in the European project PRIMA and ANR project DISCO.

In June 2010, I became co-director of the French network for complex systems (Réseau National des Systèmes Complexes).

The book I edited with Nigel Gilbert from the Patres project: Viability and Resilience of Complex Systems: more info.

Recent publications

Journal Articles (25)

H. Mahboubi, S. Bimonte, G. Deffuant
Analyzing demographic and economic simulation model results: a semi-automatic spatial OLAP approach
Lecture Notes in Computer Science 6782, 2011
abs doi web bib

In this paper, we present a semi-automatic SOLAP approach specially dedicated to the analysis of spatial model simulation results. We illustrate it on demographic and economic data of rural municipalities resulting from a model developed in the context of the european project PRIMA.
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@article{PUB00033066, author = {Mahboubi, H. and Bimonte, S. and Deffuant, G.}, title = {Analyzing demographic and economic simulation model results: a semi-automatic spatial OLAP approach}, title = {Analyse des résultats de modèles de simulation démographiques et économiques : une approche OLAP Spatial semi-automatique }, journal = {Lecture Notes in Computer Science}, volume = {6782}, pages = {17-31}, url = {http://cemadoc.irstea.fr/cemoa/PUB00033066}, doi = {http://dx.doi.org/10.1007/978-3-642-21928-3_2}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR TSCF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {In this paper, we present a semi-automatic SOLAP approach specially dedicated to the analysis of spatial model simulation results. We illustrate it on demographic and economic data of rural municipalities resulting from a model developed in the context of the european project PRIMA.}, }
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L. Chapel, X. Castello, C. Bernard, G. Deffuant, V. Eguiluz, S. Martin, M. San Miguel
Viability and resilience of languages in competition
PLoS One 5 (1 (e8681)), 2010
abs pdf doi web bib

We study the viability and resilience of languages, using a simple dynamical model of two languages in competition. Assuming that public action can modify the prestige of a language in order to avoid language extinction, we analyze two cases: (i) the prestige can only take two values, (ii) it can take any value but its change at each time step is bounded. In both cases, we determine the viability kernel, that is, the set of states for which there exists an action policy maintaining the coexistence of the two languages, and we define such policies. We also study the resilience of the languages and identify configurations from where the system can return to the viability kernel (definite resilience), or where one of the languages is lead to disappear (zero resilience). Within our current framework, the maintenance of a bilingual society is shown to be possible by introducing the prestige of a language as a control variable.
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@article{PUB00027990, author = {Chapel, L. and Castello, X. and Bernard, C. and Deffuant, G. and Eguiluz, V. and Martin, S. and San Miguel, M.}, title = {Viability and resilience of languages in competition}, title = {Viabilité et résilience de langues en compétitions}, journal = {PLoS One}, volume = {5}, number = {1 (e8681)}, pages = {11}, pdf = {http://motive.cemagref.fr/_publication/PUB00027990.pdf}, url = {http://www.plosone.org/article/info:doi/10.1371/journal.pone.0008681}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00027990}, doi = {http://dx.doi.org/10.1371/journal.pone.0008681}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; IFISC ESP ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; IFISC ESP ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; IFISC ESP}, abstract = {We study the viability and resilience of languages, using a simple dynamical model of two languages in competition. Assuming that public action can modify the prestige of a language in order to avoid language extinction, we analyze two cases: (i) the prestige can only take two values, (ii) it can take any value but its change at each time step is bounded. In both cases, we determine the viability kernel, that is, the set of states for which there exists an action policy maintaining the coexistence of the two languages, and we define such policies. We also study the resilience of the languages and identify configurations from where the system can return to the viability kernel (definite resilience), or where one of the languages is lead to disappear (zero resilience). Within our current framework, the maintenance of a bilingual society is shown to be possible by introducing the prestige of a language as a control variable.}, }
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F. Chuffart, N. Dumoulin, T. Faure, G. Deffuant
SimExplorer: programming experimental design on models and managing quality of modelling process
International Journal of Agricultural and Environmental Information Systems IJAEIS 1 (1), 2010
abs doi web bib

This article describes Simexplorer, a computer framework for managing simulation experiments and, to some extent, the scientific quality of the modelling process. An information system, included in the framework, insures the traceability of the experiments and their reproducibility and thus contributes to the modelling process quality management. Moreover, this information system provides facilities for sharing and exchanging components of experiment scenarios. The authors illustrate the use of the framework on a simple example of modelling process.
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@article{PUB00028275, author = {Chuffart, F. and Dumoulin, N. and Faure, T. and Deffuant, G.}, title = {SimExplorer: programming experimental design on models and managing quality of modelling process}, title = {SimExplorer : programmer des plans d'expérience sur les modèles et gérer la traçabilité des expériences}, journal = {International Journal of Agricultural and Environmental Information Systems IJAEIS}, volume = {1}, number = {1}, pages = {55-68}, url = {http://cemadoc.irstea.fr/cemoa/PUB00028275}, doi = {http://dx.doi.org/10.4018/jaeis.2010101304}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {This article describes Simexplorer, a computer framework for managing simulation experiments and, to some extent, the scientific quality of the modelling process. An information system, included in the framework, insures the traceability of the experiments and their reproducibility and thus contributes to the modelling process quality management. Moreover, this information system provides facilities for sharing and exchanging components of experiment scenarios. The authors illustrate the use of the framework on a simple example of modelling process. }, }
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G. Deffuant, S. Huet
Collective increase of first impression bias
Complexity 15 (5), 2010
abs web bib

We propose a simple model of first impression bias (FIB), where agents tend to ignore features which contradict their initial view. We consider a population of agents which are all in contact with a media, communicating randomly chosen features of an object. In some cases, we observe on simulations that FIB is significantly more frequent when the agents interact with each other than when they are only in contact with the media. We design an analytical aggregated model of the global agent-based model behaviour which helps to explain the higher number of FIB due to the interactions.
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@article{PUB00026808, author = {Deffuant, G. and Huet, S.}, title = {Collective increase of first impression bias}, title = {Effets amplificateurs de l'interaction sur le biais de primauté}, journal = {Complexity}, volume = {15}, number = {5}, pages = {25-33}, url = {http://www3.interscience.wiley.com}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00026808}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {We propose a simple model of first impression bias (FIB), where agents tend to ignore features which contradict their initial view. We consider a population of agents which are all in contact with a media, communicating randomly chosen features of an object. In some cases, we observe on simulations that FIB is significantly more frequent when the agents interact with each other than when they are only in contact with the media. We design an analytical aggregated model of the global agent-based model behaviour which helps to explain the higher number of FIB due to the interactions.}, }
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F. Gargiulo, S. Ternès, S. Huet, G. Deffuant
An iterative approach for generating statistically realistic populations of households
PLoS One 5 (1), 2010
abs pdf doi web bib

Many different simulation frameworks, in different topics, need to treat realistic datasets to initialize and calibrate the system. A precise reproduction of initial states is extremely important to obtain reliable forecast from the model. This paper proposes an algorithm to create an artificial population where individuals are described by their age, and are gathered in households respecting a variety of statistical constraints (distribution of household types, sizes, age of household head, difference of age between partners and among parents and children). Such a population is often the initial state of microsimulation or (agent) individual-based models. To get a realistic distribution of households is often very important, because this distribution has an impact on the demographic evolution. Usual techniques from microsimulation approach cross different sources of aggregated data for generating individuals. In our case the number of combinations of different households (types, sizes, age of participants) makes it computationally difficult to use directly such methods. Hence we developed a specific algorithm to make the problem more easily tractable. We generate the populations of two pilot municipalities in Auvergne region (France) to illustrate the approach. The generated populations show a good agreement with the available statistical datasets (not used for the generation) and are obtained in a reasonable computational time. / Dans beaucoup de domaines, la simulation nécessite le traitement de données réalistes pour initialiser et calibrer le système. Une reproduction précise de l'état initial contribue largement à l'obtention de prédictions fiables. Ce papier propose un algorithme de création d'une population artificielle composée d'individus décrits par leur âge. Ces individus sont membres de ménages qui respectent une variété de contraintes statistiques (distribution des types de ménages, différences d'âge dans les couples ou entre parents et enfants). Une telle population sert souvent d'état initial pour un modèle de microsimulation ou un modèle agent (ou individus-centré). La qualité de la distribution des ménages est importantes car cette distribution a un impact sur l'évolution démographique. Les techniques usuelles de microsimulation croisent différentes sources de données à des niveaux agrégés pour générer les individus. Dans notre cas, le nombre de combinaisons de différents ménages (types, taille, âge des membres) interdit une telle approche du fait de sa difficulté computationnelle. Nous proposons donc un algorithme permettant la génération relativement rapide et simple d'une telle population. Nous générons la population de deux municipalités Auvergnates pour illustrer l'approche. Les populations générées sont évaluées de bonne qualité par confrontation à des propriétés statistiques - non utilisées pour la génération - des communes qu'elles représentent. Elles sont obtenues en un temps raisonnable.
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@article{PUB00027953, author = {Gargiulo, F. and Ternès, S. and Huet, S. and Deffuant, G.}, title = {An iterative approach for generating statistically realistic populations of households}, title = {Une approche itérative pour la génération de populations de ménages réalistes du point de vue statistique}, journal = {PLoS One}, volume = {5}, number = {1}, pages = {9}, pdf = {http://motive.cemagref.fr/_publication/PUB00027953.pdf}, url = {http://www.plosone.org/article/info:doi/10.1371/journal.pone.0008828}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00027953}, doi = {http://dx.doi.org/10.1371/journal.pone.0008828 }, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {Many different simulation frameworks, in different topics, need to treat realistic datasets to initialize and calibrate the system. A precise reproduction of initial states is extremely important to obtain reliable forecast from the model. This paper proposes an algorithm to create an artificial population where individuals are described by their age, and are gathered in households respecting a variety of statistical constraints (distribution of household types, sizes, age of household head, difference of age between partners and among parents and children). Such a population is often the initial state of microsimulation or (agent) individual-based models. To get a realistic distribution of households is often very important, because this distribution has an impact on the demographic evolution. Usual techniques from microsimulation approach cross different sources of aggregated data for generating individuals. In our case the number of combinations of different households (types, sizes, age of participants) makes it computationally difficult to use directly such methods. Hence we developed a specific algorithm to make the problem more easily tractable. We generate the populations of two pilot municipalities in Auvergne region (France) to illustrate the approach. The generated populations show a good agreement with the available statistical datasets (not used for the generation) and are obtained in a reasonable computational time. / Dans beaucoup de domaines, la simulation nécessite le traitement de données réalistes pour initialiser et calibrer le système. Une reproduction précise de l'état initial contribue largement à l'obtention de prédictions fiables. Ce papier propose un algorithme de création d'une population artificielle composée d'individus décrits par leur âge. Ces individus sont membres de ménages qui respectent une variété de contraintes statistiques (distribution des types de ménages, différences d'âge dans les couples ou entre parents et enfants). Une telle population sert souvent d'état initial pour un modèle de microsimulation ou un modèle agent (ou individus-centré). La qualité de la distribution des ménages est importantes car cette distribution a un impact sur l'évolution démographique. Les techniques usuelles de microsimulation croisent différentes sources de données à des niveaux agrégés pour générer les individus. Dans notre cas, le nombre de combinaisons de différents ménages (types, taille, âge des membres) interdit une telle approche du fait de sa difficulté computationnelle. Nous proposons donc un algorithme permettant la génération relativement rapide et simple d'une telle population. Nous générons la population de deux municipalités Auvergnates pour illustrer l'approche. Les populations générées sont évaluées de bonne qualité par confrontation à des propriétés statistiques - non utilisées pour la génération - des communes qu'elles représentent. Elles sont obtenues en un temps raisonnable.}, }
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S. Huet, G. Deffuant
Openness leads to opinion stability and narrowness to volatility
Advances in Complex Systems 13 (3), 2010
abs pdf doi bib

We propose a new opinion dynamic model based on the experiments and results of Wood et al (1996). We consider pairs of individuals discussing on two attitudinal dimensions, and we suppose that one dimension is important, the other secondary. The dynamics are mainly ruled by the level of agreement on the main dimension. If two individuals are close on the main dimension, then they attract each other on the main and on the secondary dimensions, whatever their disagreement on the secondary dimension. If they are far from each other on the main dimension, then too much proximity on the secondary dimension is uncomfortable, and generates rejection on this dimension. The proximity is defined by comparing the opinion distance with a threshold called attraction threshold on the main dimension and rejection threshold on the secondary dimension. With such dynamics, a population with opinions initially uniformly drawn evolves to a set of clusters, inside which secondary opinions fluctuate more or less depending on threshold values. We observe that a low attraction threshold favours fluctuations on the secondary dimension, especially when the rejection threshold is high. The opinion evolutions of the model can be related to some stylised facts.
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@article{PUB00029104, author = {Huet, S. and Deffuant, G.}, title = {Openness leads to opinion stability and narrowness to volatility}, title = {L'ouverture d'esprit entraîne la stabilité des opinions tandis que le contraire entraîne leur volatilité}, journal = {Advances in Complex Systems}, volume = {13}, number = {3}, pages = {405-423}, pdf = {http://motive.cemagref.fr/_publication/PUB00029104.pdf}, doi = {http://dx.doi.org/10.1142/10.1142/S0219525910002633}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {We propose a new opinion dynamic model based on the experiments and results of Wood et al (1996). We consider pairs of individuals discussing on two attitudinal dimensions, and we suppose that one dimension is important, the other secondary. The dynamics are mainly ruled by the level of agreement on the main dimension. If two individuals are close on the main dimension, then they attract each other on the main and on the secondary dimensions, whatever their disagreement on the secondary dimension. If they are far from each other on the main dimension, then too much proximity on the secondary dimension is uncomfortable, and generates rejection on this dimension. The proximity is defined by comparing the opinion distance with a threshold called attraction threshold on the main dimension and rejection threshold on the secondary dimension. With such dynamics, a population with opinions initially uniformly drawn evolves to a set of clusters, inside which secondary opinions fluctuate more or less depending on threshold values. We observe that a low attraction threshold favours fluctuations on the secondary dimension, especially when the rejection threshold is high. The opinion evolutions of the model can be related to some stylised facts.}, }
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N. Mabrouk, G. Deffuant, T. Tolker Nielsen, C. Lobry
Bacteria can form interconnected microcolonies when a self-excreted product reduces their surface motility: evidence from individual-based model simulations
Theory in Biosciences 129 (1), 2010
abs pdf bib

Recent experimental observations of Pseudomonas aeruginosa, a model bacterium in biofilm research, reveal that, under specific growth conditions, bacterial cells form patterns of interconnected microcolonies. In the present work, we use an individual-based model to assess the involvement of bacteria motility and self-produced extracellular substance in the formation of these patterns. In our simulations, the pattern of interconnected microcolonies appears only when bacteria motility is reduced by excreted extracellular macromolecules. Immotile bacteria form isolated microcolonies and constantly motile bacteria form flat biofilms. Based on experimental data and computer simulations, we suggest a mechanism that could be responsible for these interconnected microcolonies. / Des observations récentes de Pseudomonas aeruginosa, une bactérie-modèle dans la recherche sur les biofilms, ont montré que sous certaines conditions cette bactérie forme des colonies interconnectées. Dans ce travail nous utilisons un modèle individus-centré pour explorer le rôle de la mobilité des bactéries et la production d'exopolymère dans la formation de ces structures. Nos simulations montrent que les microcolonies interconnectées se forment lorsque la mobilité des bactéries est réduite par l'excrétion de ma cromolécules. Les bactéries immobiles forment des microcolonies isolées et les bactéries mobiles forment des biofilms plats. En se basant sur les observations expérimentales et les simulations numériques nous suggérant que la réduction de la mobilité des bactéries par la production d'exopolymère pourrait être responsable de ces structures.
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@article{PUB00027304, author = {Mabrouk, N. and Deffuant, G. and Tolker Nielsen, T. and Lobry, C.}, title = {Bacteria can form interconnected microcolonies when a self-excreted product reduces their surface motility: evidence from individual-based model simulations}, title = {Modélisation individus-centrée de la formation de colonies connectées dans un système de bactéries mobiles excrétant un exopolymère qui réduit leur mobilité}, journal = {Theory in Biosciences}, volume = {129}, number = {1}, pages = {1-13}, pdf = {http://motive.cemagref.fr/_publication/PUB00027304.pdf}, year = {2010}, affiliation = {INRIA MONTPELLIER MERE PROJECT FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; UNIVERSITY OF COPENHAGEN DEPARTMENT OF INTERNATIONAL HEALTH DNK ; INRIA MONTPELLIER MERE PROJECT FRA}, ISBNISSN = {ISSN: 1431-7613 }, abstract = {Recent experimental observations of Pseudomonas aeruginosa, a model bacterium in biofilm research, reveal that, under specific growth conditions, bacterial cells form patterns of interconnected microcolonies. In the present work, we use an individual-based model to assess the involvement of bacteria motility and self-produced extracellular substance in the formation of these patterns. In our simulations, the pattern of interconnected microcolonies appears only when bacteria motility is reduced by excreted extracellular macromolecules. Immotile bacteria form isolated microcolonies and constantly motile bacteria form flat biofilms. Based on experimental data and computer simulations, we suggest a mechanism that could be responsible for these interconnected microcolonies. / Des observations récentes de Pseudomonas aeruginosa, une bactérie-modèle dans la recherche sur les biofilms, ont montré que sous certaines conditions cette bactérie forme des colonies interconnectées. Dans ce travail nous utilisons un modèle individus-centré pour explorer le rôle de la mobilité des bactéries et la production d'exopolymère dans la formation de ces structures. Nos simulations montrent que les microcolonies interconnectées se forment lorsque la mobilité des bactéries est réduite par l'excrétion de ma cromolécules. Les bactéries immobiles forment des microcolonies isolées et les bactéries mobiles forment des biofilms plats. En se basant sur les observations expérimentales et les simulations numériques nous suggérant que la réduction de la mobilité des bactéries par la production d'exopolymère pourrait être responsable de ces structures.}, }
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H. Mahboubi, T. Faure, S. Bimonte, G. Deffuant, J.P. Chanet, F. Pinet
A multidimensional model for data warehouses of simulation results
International Journal of Agricultural and Environmental Information Systems IJAEIS 1 (2), 2010
abs doi web bib

This paper deals with the multidimensional modeling of a data warehouse for simulation results. It aims at answering new needs for data management which appear when exploring complex simulation models. Indeed, testing different parameter values and different versions of such models produces a huge volume of data, especially when simulations cover long time periods. These data must often be studied extensively at different levels of aggregation. We propose a generic multidimensional schema to analyze the results of a simulation model. This schema can guide modelers in designing specific data warehouses. We also propose an adaptation of an OLAP client tool in order to provide an adequate visualization of data. As an example, we implement a data warehouse for the analysis of results produced from a savanna simulation model, using a Relational OLAP architecture.
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@article{PUB00029041, author = {Mahboubi, H. and Faure, T. and Bimonte, S. and Deffuant, G. and Chanet, J.P. and Pinet, F.}, title = {A multidimensional model for data warehouses of simulation results }, title = {Un modèle multidimensionnel pour les entrepôts de résultats de simulation}, journal = {International Journal of Agricultural and Environmental Information Systems IJAEIS}, volume = {1}, number = {2}, pages = {1-19}, url = {http://cemadoc.irstea.fr/cemoa/PUB00029041}, doi = {http://dx.doi.org/10.4018/jaeis.2010070101}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR TSCF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR TSCF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR TSCF FRA ; CEMAGREF CLERMONT FERRAND UR TSCF FRA}, abstract = {This paper deals with the multidimensional modeling of a data warehouse for simulation results. It aims at answering new needs for data management which appear when exploring complex simulation models. Indeed, testing different parameter values and different versions of such models produces a huge volume of data, especially when simulations cover long time periods. These data must often be studied extensively at different levels of aggregation. We propose a generic multidimensional schema to analyze the results of a simulation model. This schema can guide modelers in designing specific data warehouses. We also propose an adaptation of an OLAP client tool in order to provide an adequate visualization of data. As an example, we implement a data warehouse for the analysis of results produced from a savanna simulation model, using a Relational OLAP architecture.}, }
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L. Chapel, G. Deffuant, S. Martin, C. Mullon
Defining yield policies in a viability approach
Ecological Modelling 212 (1-2), 2008
abs pdf doi bib

Mullon et al. [Mullon, C., Curry, P., Shannon, L., 2004. Viability model of trophic interactions in marine ecosystems. Nat. Resour. Model. 17 (1), 2758] proposed a dynamical model of biomass evolution in the Southern Benguela ecosystem, including five different groups (detritus, phytoplankton, zooplankton, pelagic fish and demersal fish). They studied this model in a viability perspective, trying to assess, for a given constant yield, whether each species biomass remains inside a given interval, taking into account the uncertainty on the interaction coefficients. Instead of studying the healthy states of this marine ecosystem with a constant yield, we focus here on the yield policies which keep the system viable. Using the mathematical concept of viability kernel, we examine how yield management might guarantee viable fisheries. One of the main practical difficulties up to now with the viability theory was the lack of methods to solve the problem in large dimensions. In this paper, we use a new method based on SVMs, which gives this theory a larger practical potential. Solving the viability problem provides all yield policies (if any) which guarantee a perennial system. We illustrate our main findings with numerical simulations.
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@article{PUB00024646, author = {Chapel, L. and Deffuant, G. and Martin, S. and Mullon, C.}, title = {Defining yield policies in a viability approach}, title = {Définir des politiques de pêche grâce à la théorie de la viabilité}, journal = {Ecological Modelling}, volume = {212}, number = {1-2}, pages = {10-15}, pdf = {http://motive.cemagref.fr/_publication/PUB00024646.pdf}, doi = {http://dx.doi.org/10.1016/j.ecolmodel.2007.10.007 }, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; IRD UR GEODES BONDY}, abstract = {Mullon et al. [Mullon, C., Curry, P., Shannon, L., 2004. Viability model of trophic interactions in marine ecosystems. Nat. Resour. Model. 17 (1), 2758] proposed a dynamical model of biomass evolution in the Southern Benguela ecosystem, including five different groups (detritus, phytoplankton, zooplankton, pelagic fish and demersal fish). They studied this model in a viability perspective, trying to assess, for a given constant yield, whether each species biomass remains inside a given interval, taking into account the uncertainty on the interaction coefficients. Instead of studying the healthy states of this marine ecosystem with a constant yield, we focus here on the yield policies which keep the system viable. Using the mathematical concept of viability kernel, we examine how yield management might guarantee viable fisheries. One of the main practical difficulties up to now with the viability theory was the lack of methods to solve the problem in large dimensions. In this paper, we use a new method based on SVMs, which gives this theory a larger practical potential. Solving the viability problem provides all yield policies (if any) which guarantee a perennial system. We illustrate our main findings with numerical simulations.}, }
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S. Huet, G. Deffuant, W. Jager
Rejection mechanism in 2D bounded confidence provides more conformity
Advances in Complex Systems 11 (4), 2008
abs pdf doi bib

This paper explores the dynamics of attitude change in 2 dimensions (2D) as a result of social interaction. We add a rejection mechanism into the 2D bounded confidence (BC) model proposed by Deffuant et al (2001). Individuals are characterised by twodimensional continuous attitudes, each associated with an uncertainty u, supposed constant in this first study. Individuals interact by random pairs. If their attitudes are closer than u on both dimensions, or further than u on both dimensions, or closer than u on one dimension and not further than u + delta u on the other dimension, then the rules of the BC model apply. But if their attitudes are closer than u on one dimension and further than u + delta u on the other dimension, then the individuals are in a dissonant state. They tend to solve it by shifting away their close attitudes. The model shows metastable clusters, which maintain themselves through opposite influences of competitor clusters. Our analysis and first experiments support the hypothesis that, for a large range of uncertainty values, the number of clusters grows linearly with the inverse of the uncertainty, whereas this growth is quadratic in the BC model.
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@article{PUB00024189, author = {Huet, S. and Deffuant, G. and Jager, W.}, title = {Rejection mechanism in 2D bounded confidence provides more conformity}, title = {Un mécanisme de rejet dans un modèle de confiance limitée 2D engendre davantage de conformité}, journal = {Advances in Complex Systems}, volume = {11}, number = {4}, pages = {529-549}, pdf = {http://motive.cemagref.fr/_publication/PUB00024189.pdf}, doi = {http://dx.doi.org/10.1142/S0219525908001799}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; FACULTY OF ECONOMICS AND BUSINESS UNIVERSITY OF GRONINGEN NLD}, abstract = {This paper explores the dynamics of attitude change in 2 dimensions (2D) as a result of social interaction. We add a rejection mechanism into the 2D bounded confidence (BC) model proposed by Deffuant et al (2001). Individuals are characterised by twodimensional continuous attitudes, each associated with an uncertainty u, supposed constant in this first study. Individuals interact by random pairs. If their attitudes are closer than u on both dimensions, or further than u on both dimensions, or closer than u on one dimension and not further than u + delta u on the other dimension, then the rules of the BC model apply. But if their attitudes are closer than u on one dimension and further than u + delta u on the other dimension, then the individuals are in a dissonant state. They tend to solve it by shifting away their close attitudes. The model shows metastable clusters, which maintain themselves through opposite influences of competitor clusters. Our analysis and first experiments support the hypothesis that, for a large range of uncertainty values, the number of clusters grows linearly with the inverse of the uncertainty, whereas this growth is quadratic in the BC model.}, }
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S. Huet, G. Deffuant
Differential equation models derived from an individual-based model can help to understand emergent effects
JASSS-The Journal of Artificial Societies and Social Simulation 11 (2), 2008
abs web bib

We study a model of primacy effect on individual's attitude. Typically, when receiving a strong negative feature first, the individual keeps a negative attitude whatever the number of moderate positive features it receives afterwards. We consider a population of individuals, which receive the features from a media, and communicate with each other. We observe that interactions favour the primacy effect, compared with a population of isolated individuals. We derive a differential equation system ruling the evolution of probabilities that individuals retain different sets of features. The study of this aggregated model of the IBM shows that interaction can increase or decrease the number of individuals exhibiting a primacy effect. We verify on the IBM that the interactions can decrease the primacy effect in the conditions suggested by the study of the aggregated model. We finally discuss the interest of such a double-modelling approach (using a model of the individual based model) for this application.
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@article{PUB00024126, author = {Huet, S. and Deffuant, G.}, title = {Differential equation models derived from an individual-based model can help to understand emergent effects}, title = {Les modèles d'équations différentielles, dérivés d'un modèle individu centré, peuvent aider à la compréhension des effets émergents}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {11}, number = {2}, pages = {16}, url = {http://jasss.soc.surrey.ac.uk/11/2/10.html}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00024126}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {We study a model of primacy effect on individual's attitude. Typically, when receiving a strong negative feature first, the individual keeps a negative attitude whatever the number of moderate positive features it receives afterwards. We consider a population of individuals, which receive the features from a media, and communicate with each other. We observe that interactions favour the primacy effect, compared with a population of isolated individuals. We derive a differential equation system ruling the evolution of probabilities that individuals retain different sets of features. The study of this aggregated model of the IBM shows that interaction can increase or decrease the number of individuals exhibiting a primacy effect. We verify on the IBM that the interactions can decrease the primacy effect in the conditions suggested by the study of the aggregated model. We finally discuss the interest of such a double-modelling approach (using a model of the individual based model) for this application.}, }
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G. Deffuant, S. Huet
Propagation effects of filtering incongruent information
Journal of Business Research 60 (8), 2007
abs web bib

This report proposes for a simple individual-based model of information filtering, while focusing in particular on some of its implications for the attitude toward an object. The model assumes that a filter selects only important features, with a higher threshold of importance when the attitude toward the feature is incongruent with the global attitude toward the object. Individuals transmit only features that are congruent with their global attitude. This article considers two variants of the model. To both applies that different orders of feature reception can lead to different attitudes. For instance, a positive attitude toward an object can at a certain point become negative, even though the object is globally neutral (the sum of the feature attitudes is zero). The interactions among individuals can significantly increase the probability of such non-rational attitudes.
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@article{PUB00021835, author = {Deffuant, G. and Huet, S.}, title = {Propagation effects of filtering incongruent information}, title = {Effet de la propagation du filtrage d'informations incongruentes}, journal = {Journal of Business Research}, volume = {60}, number = {8}, pages = {816-825}, url = {http://cemadoc.irstea.fr/cemoa/PUB00021835}, year = {2007}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {This report proposes for a simple individual-based model of information filtering, while focusing in particular on some of its implications for the attitude toward an object. The model assumes that a filter selects only important features, with a higher threshold of importance when the attitude toward the feature is incongruent with the global attitude toward the object. Individuals transmit only features that are congruent with their global attitude. This article considers two variants of the model. To both applies that different orders of feature reception can lead to different attitudes. For instance, a positive attitude toward an object can at a certain point become negative, even though the object is globally neutral (the sum of the feature attitudes is zero). The interactions among individuals can significantly increase the probability of such non-rational attitudes.}, }
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S. Huet, M. Edwards, G. Deffuant
Taking into account the variations of neighbourhood sizes in the mean-field approximation of the threshold model on a random network
JASSS-The Journal of Artificial Societies and Social Simulation 10 (1), 2007
abs web bib

We compare the individual-based "threshold model" of innovation diffusion in the version which has been studied by Young (1998), with an aggregate model we derived from it. This model allows us to formalise and test hypotheses on the influence of individual characteristics upon global evolution. The classical threshold model supposes that an individual adopts a behaviour according to a trade-off between a social pressure and a personal interest. Our study considers only the case where all have the same threshold. We present an aggregated model, which takes into account variations of the neighbourhood sizes, whereas previous work assumed this size fixed (Edwards et al. 2003a). The comparison between the aggregated models (the first one assuming a neighbourhood size and the second one, a variable one) points out an improvement of the approximation in most of the value of parameter space. This proves that the average degree of connectivity (first aggregated model) is not sufficient for characterising the evolution, and that the node degree variability has an impact on the diffusion dynamics. Remaining differences between both models give us some clues about the specific ability of individual-based model to maintain a minority behaviour which becomes a majority by an addition of stochastic effects.
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@article{PUB00021336, author = {Huet, S. and Edwards, M. and Deffuant, G.}, title = {Taking into account the variations of neighbourhood sizes in the mean-field approximation of the threshold model on a random network }, title = {Prendre en compte les variations de taille de voisinage social au sein d'une approximation par champ moyen d'un modèle à seuil sur un réseau aléatoire}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {10}, number = {1}, pages = {15}, url = {http://jasss.soc.surrey.ac.uk/10/1/10.html}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00021336}, year = {2007}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {We compare the individual-based "threshold model" of innovation diffusion in the version which has been studied by Young (1998), with an aggregate model we derived from it. This model allows us to formalise and test hypotheses on the influence of individual characteristics upon global evolution. The classical threshold model supposes that an individual adopts a behaviour according to a trade-off between a social pressure and a personal interest. Our study considers only the case where all have the same threshold. We present an aggregated model, which takes into account variations of the neighbourhood sizes, whereas previous work assumed this size fixed (Edwards et al. 2003a). The comparison between the aggregated models (the first one assuming a neighbourhood size and the second one, a variable one) points out an improvement of the approximation in most of the value of parameter space. This proves that the average degree of connectivity (first aggregated model) is not sufficient for characterising the evolution, and that the node degree variability has an impact on the diffusion dynamics. Remaining differences between both models give us some clues about the specific ability of individual-based model to maintain a minority behaviour which becomes a majority by an addition of stochastic effects.}, }
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G. Deffuant
Comparing extremism propagation patterns in continuous opinion models
JASSS-The Journal of Artificial Societies and Social Simulation 9 (3), 2006
abs web bib

We compare patterns of extremism propagation yielded by 4 continuous opinion models, when the main parameters vary, on different types of networks (total connection, random network, lattice). In two models the individuals take into account the uncertainty of their interlocutor, and they show similar patterns, with a higher probability of double extreme convergence than in the other couple of models (in which the interlocutor's uncertainty is not taken into account). The addition of noise does not change significantly the results, except that it favours the single extreme convergence in some models. The lattice topology of interactions provides results which are significantly different from the ones obtained with a random network of similar connection density. We identify 3 typical behaviours with a single initial extremist, which help to explain the different results. In particular, we observe that the single extreme convergence is favoured by small shortest paths between all pairs of nodes in the network.
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@article{PUB00020398, author = {Deffuant, G.}, title = {Comparing extremism propagation patterns in continuous opinion models}, title = {Formes de propagation de l'extrémisme dans des modèles d'opinions continues}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {9}, number = {3}, pages = {24}, url = {http://jasss.soc.surrey.ac.uk/9/3/8.html}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00020398}, year = {2006}, affiliation = {CEMAGREF CLERMONT FERRAND LICF}, abstract = {We compare patterns of extremism propagation yielded by 4 continuous opinion models, when the main parameters vary, on different types of networks (total connection, random network, lattice). In two models the individuals take into account the uncertainty of their interlocutor, and they show similar patterns, with a higher probability of double extreme convergence than in the other couple of models (in which the interlocutor's uncertainty is not taken into account). The addition of noise does not change significantly the results, except that it favours the single extreme convergence in some models. The lattice topology of interactions provides results which are significantly different from the ones obtained with a random network of similar connection density. We identify 3 typical behaviours with a single initial extremist, which help to explain the different results. In particular, we observe that the single extreme convergence is favoured by small shortest paths between all pairs of nodes in the network. }, }
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G. Deffuant, S. Moss, W. Jager
Dialogues concerning a (possibly) new science
JASSS-The Journal of Artificial Societies and Social Simulation 9 (1), 2006
abs web bib

The paper relates virtual dialogues about social simulation, with the implicit reference to Galieo's 'dialogues concerning two new sciences'.
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@article{PUB00020397, author = {Deffuant, G. and Moss, S. and Jager, W.}, title = {Dialogues concerning a (possibly) new science}, title = {Dialogues à propos d'une (possible) nouvelle science}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {9}, number = {1}, pages = {7}, url = {http://jasss.soc.surrey.ac.uk/9/1/1.html}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00020397}, year = {2006}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; MANCHESTER METROPOLITAN UNIVERSITY GBR ; UNIVERSITY OF GRONINGEN NLD}, abstract = {The paper relates virtual dialogues about social simulation, with the implicit reference to Galieo's 'dialogues concerning two new sciences'.}, }
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G. Deffuant, S. Huet, F. Amblard
An individual-based model of innovation diffusion mixing social influence and rational anticipation
American Journal of Sociology 110 (4), 2005
abs web bib

We propose an individual-based model of innovation diffusion and explore its main dynamical properties. In the model, individuals give an a priori social value to the innovation, which evolves during their interactions with the Relative agreement influence model. This model offers the possibility of including a minority of extremists, with extreme and very certain opinions. Individuals who give a good social value to the innovation, tend to look for information which allows them to evaluate a more precise individual benefit of the adoption. They can get such information from their associates or from the media. If their social value is bad, neither they consider the information or transmit it. Individuals adopt the innovation if the overall evaluation including the social value and the individual benefit is good enough with a sufficient certainty. The main result of the model exploration is that innovations with high social values and bad individual benefit have more chances to succeed, than innovations with bad social value and high individual benefit. Moreover, in some cases, a minority of extremists can have a very important impact on the propagation, by polarizing the social value. / Nous proposons un modèle individu-centré de diffusion de l'innovation et explorons ses principales propriétés dynamiques. Dans notre modèle, les individus donnent une valeur sociale a priori à l'innovation. Cette valeur évolue durant les interactions entre les individus selon le modèle d'influence "Relative agreement". Ce modèle permet de prendre en compte les minorités dotées d'opinions extrêmes et certaines. Les individus pensant l'innovation bonne socialement recherchent l'information qui leur permettra d'évaluer précisément l'impact à titre personnel de l'adoption. Une telle information peut être disponible auprès d'un de leur collègue ou des medias. Lorsqu'ils pensent l'innovation mauvaise socialement, ils ne considèrent pas l'information et ne la transmettent pas. Les individus adoptent l'innovation si l'évaluation globale (incluant valeur sociale et impact à titre personnel) est suffisamment positive avec une certitude suffisante. Le résultat principal de l'exploration du modèle est que les innovations dotées d'une valeur sociale forte et d'un impact personnel mauvais ont davantage de chances d'être adoptées que les innovations dotées d'une mauvaise valeur sociale et d'un impact personnel bon. Par ailleurs, dans certains cas, une minorité d'extrémistes peut avoir un impact important sur la diffusion en diffusant à tous leurs opinions extrêmes sur la valeur sociale positive de l'innovation.
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@article{PUB00018516, author = {Deffuant, G. and Huet, S. and Amblard, F.}, title = {An individual-based model of innovation diffusion mixing social influence and rational anticipation}, title = {Un modèle individu-centré de diffusion de l'innovation mixant influence sociale et anticipation rationnelle}, journal = {American Journal of Sociology}, volume = {110}, number = {4}, pages = {1041-1069}, url = {http://cemadoc.irstea.fr/cemoa/PUB00018516}, year = {2005}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {We propose an individual-based model of innovation diffusion and explore its main dynamical properties. In the model, individuals give an a priori social value to the innovation, which evolves during their interactions with the Relative agreement influence model. This model offers the possibility of including a minority of extremists, with extreme and very certain opinions. Individuals who give a good social value to the innovation, tend to look for information which allows them to evaluate a more precise individual benefit of the adoption. They can get such information from their associates or from the media. If their social value is bad, neither they consider the information or transmit it. Individuals adopt the innovation if the overall evaluation including the social value and the individual benefit is good enough with a sufficient certainty. The main result of the model exploration is that innovations with high social values and bad individual benefit have more chances to succeed, than innovations with bad social value and high individual benefit. Moreover, in some cases, a minority of extremists can have a very important impact on the propagation, by polarizing the social value. / Nous proposons un modèle individu-centré de diffusion de l'innovation et explorons ses principales propriétés dynamiques. Dans notre modèle, les individus donnent une valeur sociale a priori à l'innovation. Cette valeur évolue durant les interactions entre les individus selon le modèle d'influence "Relative agreement". Ce modèle permet de prendre en compte les minorités dotées d'opinions extrêmes et certaines. Les individus pensant l'innovation bonne socialement recherchent l'information qui leur permettra d'évaluer précisément l'impact à titre personnel de l'adoption. Une telle information peut être disponible auprès d'un de leur collègue ou des medias. Lorsqu'ils pensent l'innovation mauvaise socialement, ils ne considèrent pas l'information et ne la transmettent pas. Les individus adoptent l'innovation si l'évaluation globale (incluant valeur sociale et impact à titre personnel) est suffisamment positive avec une certitude suffisante. Le résultat principal de l'exploration du modèle est que les innovations dotées d'une valeur sociale forte et d'un impact personnel mauvais ont davantage de chances d'être adoptées que les innovations dotées d'une mauvaise valeur sociale et d'un impact personnel bon. Par ailleurs, dans certains cas, une minorité d'extrémistes peut avoir un impact important sur la diffusion en diffusant à tous leurs opinions extrêmes sur la valeur sociale positive de l'innovation. }, }
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L. Rousseau, G. Deffuant
Gestion des territoires : aider à la formulation collective des problèmes
Natures, Sciences et Sociétés 13 (1), 2005
abs web bib

Making decisions about land and water management and about urban planning in Europe involves an increasingly diverse range of actors representing heterogeneous stakes, skills and legitimacy. This situation emphasizes the importance of organizing a stage specifically devoted to problem formulation in the negotiation process. The facilitators and institutions managing the discussions are therefore keenly interested in methods and tools that help integrate the viewpoints of each actor into a common problem'. Our research aims to provide such tools and methods. We propose a conceptual framework in which the problem formulation process involves nested and alternating cycles of individual viewpoint elaboration and group discussions, confronting individual viewpoints. Our framework emphasises the crucial role of viewpoint comparison to link individual and group processes. In order to facilitate such comparisons, we suppose that viewpoints include a model of the territory and an evaluation (or preference) model. A viewpoint takes as input a hypothetical set of actions and yields as output the set of probable consequences of these actions, and the actor's evaluation (preference) of these consequences. We argue that the use of such viewpoints and comparison helps to progressively clarify the viewpoints through the discussion, to define a collective problem and to organize interactions. Following this framework, we defined and tested an operational method and a software tool called SICOPTER. The operational method organizes the whole process into phases based on simple paper representations of viewpoints and problems. SICOPTER enables the actors express their preferences about the results of expert territory models, and compare them with other stakeholders' ones, via computer representations. We present and discuss a set of tests that confirm the interest of viewpoint comparisons to facilitate group problem formulations. / La législation définissant les procédures de gestion des territoires impose de prendre en compte des enjeux d'acteurs représentatifs des différentes composantes du territoire. Nous présentons un cadre de formalisation de cette prise en compte qui fournit aux décideurs et animateurs une description systématique des problèmes définis lors de la procédure et une synthèse de la définition du territoire. Ces deux produits permettent à l'animateur de proposer de nouvelles actions possibles à la discussion et l'évaluation des acteurs. Chaque acteur construit son point de vue décrivant les conséquences de ces actions et l'évaluation que l'acteur en fait, puis le rend public. La comparaison de ces points de vue dans un cadre privé, d'une part, puis la discussion autour du résultat des comparaisons des points de vue publics, d'autre part, forment un cycle de formulation des problèmes parcourus autant que nécessaire. Le cadre est évalué par le test de deux outils dérivés.
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@article{PUB00018533, author = {Rousseau, L. and Deffuant, G.}, title = {Gestion des territoires : aider à la formulation collective des problèmes}, title = {Integrated group problem formulation}, journal = {Natures, Sciences et Sociétés}, volume = {13}, number = {1}, pages = {21-32}, url = {http://cemadoc.irstea.fr/cemoa/PUB00018533}, year = {2005}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {Making decisions about land and water management and about urban planning in Europe involves an increasingly diverse range of actors representing heterogeneous stakes, skills and legitimacy. This situation emphasizes the importance of organizing a stage specifically devoted to problem formulation in the negotiation process. The facilitators and institutions managing the discussions are therefore keenly interested in methods and tools that help integrate the viewpoints of each actor into a common problem'. Our research aims to provide such tools and methods. We propose a conceptual framework in which the problem formulation process involves nested and alternating cycles of individual viewpoint elaboration and group discussions, confronting individual viewpoints. Our framework emphasises the crucial role of viewpoint comparison to link individual and group processes. In order to facilitate such comparisons, we suppose that viewpoints include a model of the territory and an evaluation (or preference) model. A viewpoint takes as input a hypothetical set of actions and yields as output the set of probable consequences of these actions, and the actor's evaluation (preference) of these consequences. We argue that the use of such viewpoints and comparison helps to progressively clarify the viewpoints through the discussion, to define a collective problem and to organize interactions. Following this framework, we defined and tested an operational method and a software tool called SICOPTER. The operational method organizes the whole process into phases based on simple paper representations of viewpoints and problems. SICOPTER enables the actors express their preferences about the results of expert territory models, and compare them with other stakeholders' ones, via computer representations. We present and discuss a set of tests that confirm the interest of viewpoint comparisons to facilitate group problem formulations. / La législation définissant les procédures de gestion des territoires impose de prendre en compte des enjeux d'acteurs représentatifs des différentes composantes du territoire. Nous présentons un cadre de formalisation de cette prise en compte qui fournit aux décideurs et animateurs une description systématique des problèmes définis lors de la procédure et une synthèse de la définition du territoire. Ces deux produits permettent à l'animateur de proposer de nouvelles actions possibles à la discussion et l'évaluation des acteurs. Chaque acteur construit son point de vue décrivant les conséquences de ces actions et l'évaluation que l'acteur en fait, puis le rend public. La comparaison de ces points de vue dans un cadre privé, d'une part, puis la discussion autour du résultat des comparaisons des points de vue publics, d'autre part, forment un cycle de formulation des problèmes parcourus autant que nécessaire. Le cadre est évalué par le test de deux outils dérivés.}, }
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G. Weisbuch, G. Deffuant, F. Amblard
Persuasion dynamics
Physica A-Statistical Mechanics and its Applications 353, 2005
abs web bib

We here discuss a model of continuous opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. We concentrate on the version of the model in the presence of few extremists which might drive the dynamics to generalised extremism. A network version of the dynamics is presented here, and its results are compared to those previously obtained for the full-mixng case. The same dynamical regimes are observed, but in rather different parameter regions. We here show that the combination of meso-scale features resulting from the first interaction steps. determines the asymptotic state of the dynamics.
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@article{PUB00018534, author = {Weisbuch, G. and Deffuant, G. and Amblard, F.}, title = {Persuasion dynamics}, title = {Dynamiques de persuasion}, journal = {Physica A-Statistical Mechanics and its Applications}, volume = {353}, pages = {27}, url = {http://cemadoc.irstea.fr/cemoa/PUB00018534}, year = {2005}, affiliation = {ECOLE NORMALE SUPERIEURE ; CEMAGREF CLERMONT FERRAND LICF ; UNIVERSITE DE TOULOUSE}, abstract = {We here discuss a model of continuous opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. We concentrate on the version of the model in the presence of few extremists which might drive the dynamics to generalised extremism. A network version of the dynamics is presented here, and its results are compared to those previously obtained for the full-mixng case. The same dynamical regimes are observed, but in rather different parameter regions. We here show that the combination of meso-scale features resulting from the first interaction steps. determines the asymptotic state of the dynamics.}, }
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F. Amblard, G. Deffuant
The role of network topology on extremism propagation with the relative agreement opinion
Physica A-Statistical Mechanics and its Applications 343, 2004
abs doi web bib

In Deffuant et al. (J. Artif. Soc. Soc. Simulation 5 (2002) 4), we proposed a simple model of opinion dynamics, which we used to simulate the influence of extremists in a population. Simulations were run without any specific interaction structure and varying the simulation parameters, we observed different attractors such as predominance of centrism, or of extremism. We even observed in certain conditions, that the whole population drifts to one extreme of the opinion, even if initially there are an equal number of extremists at each extreme of the opinion axis. In the present paper, we study the influence of the social networks on the presence of such a dynamical behavior. In particular, we use small-world networks with variable connectivity and randomness of the connections. We find that the drift to a single extreme appears only beyond a critical level of connectivity, which decreases when the randomness increases.
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@article{PUB00015776, author = {Amblard, F. and Deffuant, G.}, title = {The role of network topology on extremism propagation with the relative agreement opinion}, journal = {Physica A-Statistical Mechanics and its Applications}, volume = {343}, pages = {725-738}, url = {http://cemadoc.irstea.fr/cemoa/PUB00015776}, doi = {http://dx.doi.org/10.1016/j.physa.2004.06.102}, year = {2004}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {In Deffuant et al. (J. Artif. Soc. Soc. Simulation 5 (2002) 4), we proposed a simple model of opinion dynamics, which we used to simulate the influence of extremists in a population. Simulations were run without any specific interaction structure and varying the simulation parameters, we observed different attractors such as predominance of centrism, or of extremism. We even observed in certain conditions, that the whole population drifts to one extreme of the opinion, even if initially there are an equal number of extremists at each extreme of the opinion axis. In the present paper, we study the influence of the social networks on the presence of such a dynamical behavior. In particular, we use small-world networks with variable connectivity and randomness of the connections. We find that the drift to a single extreme appears only beyond a critical level of connectivity, which decreases when the randomness increases.}, }
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G. Deffuant, G. Weisbuch, F. Amblard, T. Faure
Simple is beautiful... and necessary
JASSS-The Journal of Artificial Societies and Social Simulation 6 (1), 2003
abs web bib

A contribution to the JASSS forum, in reaction to the paper in Frankfurter Allgemeine Zeitung about our model of extremism. / Une contribution au forum de JASSS, en réaction à l'article du Frankfurter Allgemeine Zeitung à propos de notre modèle de l'extrémisme.
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@article{PUB00011230, author = {Deffuant, G. and Weisbuch, G. and Amblard, F. and Faure, T.}, title = {Simple is beautiful... and necessary}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {6}, number = {1}, pages = {4}, url = {http://jasss.soc.surrey.ac.uk/6/1/6.html}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00011230}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; ECOLE NORMALE SUPERIEURE LABORATOIRE DE PHYSIQUE STATISTIQUE PARIS ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, number = {03/0007}, abstract = {A contribution to the JASSS forum, in reaction to the paper in Frankfurter Allgemeine Zeitung about our model of extremism. / Une contribution au forum de JASSS, en réaction à l'article du Frankfurter Allgemeine Zeitung à propos de notre modèle de l'extrémisme.}, }
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M. Edwards, S. Huet, F. Goreaud, G. Deffuant
Comparing an individual-based model of behaviour diffusion with its mean field aggregate approximation.
JASSS-The Journal of Artificial Societies and Social Simulation 6 (4), 2003
abs web bib

In this paper we compare a version of the individual-based 'threshold model' of innovation diffusion with an aggregate deterministic model that we constructed from it. The classical threshold model supposes that an individual adopts a behaviour according to a trade-off between a social pressure (the number of neighbours adopting the behaviour) and a personal interest or resistance to change (the threshold). The aggregate model makes approximations in order to estimate the evolution of groups of individuals with the same number of neighbours of similar behaviour. We compare both models at different points of the parameter space. We find that the aggregate model gives a good approximation of the individual in some cases; however in other cases the behaviour of the aggregate approximation differs. Using theoretical interpretation of this difference based on a study of the attractors of the aggregate model, we hypothesise that the two models have the same behaviour when the aggregate model has only one attractor and that differences can occur when it has two. / Nous comparons un modèle individu-centré à seuil de diffusion de l'innovation (Valente 1995) dans la version étudiée par P. Young, et un modèle agrégé déterministe que nous avons construit en cohérence. Le modèle classique de diffusion de l'innovation à seuil suppose qu'un individu adopte un comportement suivant un compromis entre la pression sociale (le nombre de ses voisins ayant adopté ce comportement) et un intérêt personnel de résistance au changement (le seuil). Le modèle agrégé fait appel à des approximations pour estimer l'évolution de groupes d'individus ayant le même nombre de voisins suivant un certain comportement. Nous comparons ces deux modèles en différents points de l'espace des paramètres. Nous trouvons que le modèle agrégé approxime bien le modèle individu-centré dans certains cas ; toutefois, il s'avère également parfois que le comportement du modèle agrégé diffère. En nous appuyant sur une interprétation théorique de cette différence, fondée sur une étude des attracteurs du modèle agrégé, nous proposons l'hypothèse que les deux modèles suivent le même comportement lorsque le modèle agrégé n'a qu'un seul attracteur, et que des différences peuvent apparaître quand il en a deux.
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@article{PUB00018793, author = {Edwards, M. and Huet, S. and Goreaud, F. and Deffuant, G.}, title = {Comparing an individual-based model of behaviour diffusion with its mean field aggregate approximation.}, title = {Comparaison d'un modèle individu-centré de diffusion de l'innovation avec son approximation par champ moyen}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {6}, number = {4}, url = {http://jasss.soc.surrey.ac.uk/6/4/9.html}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00018793}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {In this paper we compare a version of the individual-based 'threshold model' of innovation diffusion with an aggregate deterministic model that we constructed from it. The classical threshold model supposes that an individual adopts a behaviour according to a trade-off between a social pressure (the number of neighbours adopting the behaviour) and a personal interest or resistance to change (the threshold). The aggregate model makes approximations in order to estimate the evolution of groups of individuals with the same number of neighbours of similar behaviour. We compare both models at different points of the parameter space. We find that the aggregate model gives a good approximation of the individual in some cases; however in other cases the behaviour of the aggregate approximation differs. Using theoretical interpretation of this difference based on a study of the attractors of the aggregate model, we hypothesise that the two models have the same behaviour when the aggregate model has only one attractor and that differences can occur when it has two. / Nous comparons un modèle individu-centré à seuil de diffusion de l'innovation (Valente 1995) dans la version étudiée par P. Young, et un modèle agrégé déterministe que nous avons construit en cohérence. Le modèle classique de diffusion de l'innovation à seuil suppose qu'un individu adopte un comportement suivant un compromis entre la pression sociale (le nombre de ses voisins ayant adopté ce comportement) et un intérêt personnel de résistance au changement (le seuil). Le modèle agrégé fait appel à des approximations pour estimer l'évolution de groupes d'individus ayant le même nombre de voisins suivant un certain comportement. Nous comparons ces deux modèles en différents points de l'espace des paramètres. Nous trouvons que le modèle agrégé approxime bien le modèle individu-centré dans certains cas ; toutefois, il s'avère également parfois que le comportement du modèle agrégé diffère. En nous appuyant sur une interprétation théorique de cette différence, fondée sur une étude des attracteurs du modèle agrégé, nous proposons l'hypothèse que les deux modèles suivent le même comportement lorsque le modèle agrégé n'a qu'un seul attracteur, et que des différences peuvent apparaître quand il en a deux.}, }
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G. Deffuant, F. Amblard, G. Weisbuch, T. Faure
How can extremism prevail? A study based on the relative agreement model
JASSS-The Journal of Artificial Societies and Social Simulation 5 (4), 2002
abs web bib

We model opinion dynamics in populations of agents with continuous opinion and uncertainty. The opinions and uncertainties are modified by random pair interactions. We propose a new model of interactions, called relative agreement model, which is a variant of the previously discussed bounded confidence. In this model, uncertainty as well as opinion can be modified by interactions. We introduce extremist agents by attributing a much lower uncertainty (and thus higher persuasion) to a small proportion of agents at the extremes of the opinion distribution. We study the evolution of the opinion distribution submitted to the relative agreement model. Depending upon the choice of parameters, the extremists can have a very local influence or attract the whole population. We propose a qualitative analysis of the convergence process based on a local field notion. The genericity of the observed results is tested on several variants of the bounded confidence model. / Nous modélisons la dynamique des opinions d'une population d'agents ayant une opinion continue et une incertitude associée, en proposant un nouveau modèle d'interaction, le modèle d'accord relatif, qui est une variante des modèles de confiance limitée précédemment discutés. Dans ce modèle, l'incertitude ainsi que l'opinion peuvent être modifiées suite aux interactions aléatoires entre des paires d'agents. Nous introduisons des agents extrémistes dans la population en attribuant une incertitude très inférieure (et ainsi une force de persuasion plus élevée) à une proportion d'agents située aux extrémités de la distribution d'opinion. Nous étudions par la suite l'évolution de la distribution d'opinions. Suivant la valeur des paramètres, les extrémistes peuvent avoir une influence très locale ou au contraire attirer la population tout entière. Nous proposons une analyse qualitative du processus de convergence basée sur la notion de champ local.
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@article{PUB00011226, author = {Deffuant, G. and Amblard, F. and Weisbuch, G. and Faure, T.}, title = {How can extremism prevail? A study based on the relative agreement model}, title = {Comment l'extrémisme règne ? Une étude basée sur le modèle d'accord relatif}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {5}, number = {4}, pages = {27}, url = {http://jasss.soc.surrey.ac.uk/5/4/1.html}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00011226}, year = {2002}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; ECOLE NORMALE SUPERIEURE LABORATOIRE DE PHYSIQUE STATISTIQUE PARIS ; - ; -}, number = {K LI02 3}, abstract = {We model opinion dynamics in populations of agents with continuous opinion and uncertainty. The opinions and uncertainties are modified by random pair interactions. We propose a new model of interactions, called relative agreement model, which is a variant of the previously discussed bounded confidence. In this model, uncertainty as well as opinion can be modified by interactions. We introduce extremist agents by attributing a much lower uncertainty (and thus higher persuasion) to a small proportion of agents at the extremes of the opinion distribution. We study the evolution of the opinion distribution submitted to the relative agreement model. Depending upon the choice of parameters, the extremists can have a very local influence or attract the whole population. We propose a qualitative analysis of the convergence process based on a local field notion. The genericity of the observed results is tested on several variants of the bounded confidence model. / Nous modélisons la dynamique des opinions d'une population d'agents ayant une opinion continue et une incertitude associée, en proposant un nouveau modèle d'interaction, le modèle d'accord relatif, qui est une variante des modèles de confiance limitée précédemment discutés. Dans ce modèle, l'incertitude ainsi que l'opinion peuvent être modifiées suite aux interactions aléatoires entre des paires d'agents. Nous introduisons des agents extrémistes dans la population en attribuant une incertitude très inférieure (et ainsi une force de persuasion plus élevée) à une proportion d'agents située aux extrémités de la distribution d'opinion. Nous étudions par la suite l'évolution de la distribution d'opinions. Suivant la valeur des paramètres, les extrémistes peuvent avoir une influence très locale ou au contraire attirer la population tout entière. Nous proposons une analyse qualitative du processus de convergence basée sur la notion de champ local.}, }
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G. Weisbuch, G. Deffuant, F. Amblard, J.P. Nadal
Interacting Agents and Continuous Opinions Dynamics
Lecture Notes in Economics and Mathematical Systems 521 (02/0815 ; K LI02 4), 2002
abs web bib

We present a model of opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. High thresholds yield convergence of opinions towards an average opinion, whereas low thresholds result in several opinion clusters. This model is further generalised to threshold heterogeneity, adaptive thresholds and binary strings of opinions. / Nous présentons un modèle de dynamique d'opinions dans lequel les agents ajustent des opinions continues en fonction de rencontres par paires aléatoires quand la différence entre leurs opinions est en dessous d'un seuil donné. Des seuils élevés conduisent à une convergence des opinions vers une opinion moyenne, alors que des seuils faibles résultent en plusieurs groupes d'opinions. Ce modèle est ensuite généralisé à des seuils hétérogènes, des seuils adaptatifs et des chaînes d'opinions binaires.
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@article{PUB00011231, author = {Weisbuch, G. and Deffuant, G. and Amblard, F. and Nadal, J.P.}, title = {Interacting Agents and Continuous Opinions Dynamics}, title = {Agents en interactions et dynamique d'opinions continues}, journal = {Lecture Notes in Economics and Mathematical Systems}, volume = {521}, pages = {225-242}, url = {http://cemadoc.irstea.fr/cemoa/PUB00011231}, year = {2002}, affiliation = {ECOLE NORMALE SUPERIEURE LABORATOIRE DE PHYSIQUE STATISTIQUE PARIS ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, number = {02/0815 ; K LI02 4}, abstract = {We present a model of opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. High thresholds yield convergence of opinions towards an average opinion, whereas low thresholds result in several opinion clusters. This model is further generalised to threshold heterogeneity, adaptive thresholds and binary strings of opinions. / Nous présentons un modèle de dynamique d'opinions dans lequel les agents ajustent des opinions continues en fonction de rencontres par paires aléatoires quand la différence entre leurs opinions est en dessous d'un seuil donné. Des seuils élevés conduisent à une convergence des opinions vers une opinion moyenne, alors que des seuils faibles résultent en plusieurs groupes d'opinions. Ce modèle est ensuite généralisé à des seuils hétérogènes, des seuils adaptatifs et des chaînes d'opinions binaires.}, }
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G. Weisbuch, G. Deffuant, F. Amblard, J.P. Nadal
Meet, discuss and segregate !
Complexity 7 (3), 2002
abs doi web bib

We present a model of opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. High thresholds yield convergence of opinions toward an average opinion, whereas low thresholds result in several opinion clusters. The model is further generalized to network interactions, theshold heterogeneity, adaptive thresholds, and binary strings of opinions. / Nous présentons un modèle de dynamique d'opinions dans lequel les agents ajustent des opinions continues suite à des rencontres binaires aléatoires quand la différence d'opinion est en dessous d'un seuil fixé. Des seuils importants conduisent à une convergence des opinions vers une opinion moyenne, alors que des seuils plus faibles résultent en plusieurs clusters d'opinions. Le modèle est ensuite généralisé à des interactions sur réseau, des seuils hétérogènes, des seuils adaptatifs et des chaines binaires d'opinions.
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@article{PUB00010879, author = {Weisbuch, G. and Deffuant, G. and Amblard, F. and Nadal, J.P.}, title = {Meet, discuss and segregate !}, journal = {Complexity}, volume = {7}, number = {3}, pages = {55-63}, url = {http://cemadoc.irstea.fr/cemoa/PUB00010879}, doi = {http://dx.doi.org/10.1002/cplx.1003}, year = {2002}, affiliation = {ECOLE NORMALE SUPERIEURE LABORATOIRE DE PHYSIQUE STATISTIQUE PARIS ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {We present a model of opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. High thresholds yield convergence of opinions toward an average opinion, whereas low thresholds result in several opinion clusters. The model is further generalized to network interactions, theshold heterogeneity, adaptive thresholds, and binary strings of opinions. / Nous présentons un modèle de dynamique d'opinions dans lequel les agents ajustent des opinions continues suite à des rencontres binaires aléatoires quand la différence d'opinion est en dessous d'un seuil fixé. Des seuils importants conduisent à une convergence des opinions vers une opinion moyenne, alors que des seuils plus faibles résultent en plusieurs clusters d'opinions. Le modèle est ensuite généralisé à des interactions sur réseau, des seuils hétérogènes, des seuils adaptatifs et des chaines binaires d'opinions.}, }
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G. Deffuant, D. Neau, F. Amblard, G. Weisbuch
Mixing beliefs among interacting agents
Advances in Complex Systems, 2001
abs web bib

We present a model of opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. High thresholds yield convergence of opinions towards an average opinion, whereas low thresholds result in several opinion clusters: members of the ame cluster share the same opinion but are no longer influenced by members of other clusters. / Nous présentons un modèle de dynamique des opinions dans lequel les agents ajustent des opinions continues en fonction de rencontres binaires aléatoires, lorsque la différence entre leurs opinions est en-dessous d'un certain seuil. Les seuils hauts conduisent à une convergence des opinions vers une opinion moyenne, alors que les seuils plus bas conduisent à plusieurs agglomérats d'opinion : les membres d'un même agglomérat partageant la même opinion mais n'étant plus influencés par les membres d'autres agglomérats.
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@article{PUB00009956, author = {Deffuant, G. and Neau, D. and Amblard, F. and Weisbuch, G.}, title = {Mixing beliefs among interacting agents}, title = {Evolution des croyances entre agents en interactions}, journal = {Advances in Complex Systems}, number = {3}, pages = {11}, url = {http://cemadoc.irstea.fr/cemoa/PUB00009956}, year = {2001}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; ECOLE NORMALE SUPERIEURE LABORATOIRE DE PHYSIQUE STATISTIQUE PARIS ; - ; -}, number = {01/0652 ; K LI01 5}, abstract = {We present a model of opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. High thresholds yield convergence of opinions towards an average opinion, whereas low thresholds result in several opinion clusters: members of the ame cluster share the same opinion but are no longer influenced by members of other clusters. / Nous présentons un modèle de dynamique des opinions dans lequel les agents ajustent des opinions continues en fonction de rencontres binaires aléatoires, lorsque la différence entre leurs opinions est en-dessous d'un certain seuil. Les seuils hauts conduisent à une convergence des opinions vers une opinion moyenne, alors que les seuils plus bas conduisent à plusieurs agglomérats d'opinion : les membres d'un même agglomérat partageant la même opinion mais n'étant plus influencés par les membres d'autres agglomérats.}, }
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Book Chapters (10)

I. Alvarez, S. Martin
Geometric robustness of viability kernels and resilience basins
Springer, 2011
doi web bib

@book{PUB00033189, author = {Alvarez, I. and Martin, S.}, author = {Deffuant, G. and Gilbert, N.}, title = {Geometric robustness of viability kernels and resilience basins}, bookTitle = {}, series = {Understanding complex systems}, publisher = {Springer}, pages = {193-218}, url = {http://cemadoc.irstea.fr/cemoa/PUB00033189}, doi = {http://dx.doi.org/10.1007/978-3-642-20423-4}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, ISBNISSN = {ISBN-13: 978-3642204227}, abstract = {}, }
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J.M. Calabrese, G. Deffuant, V. Grimm
Bridging the gap between computational models and viability based resilience in Savanna ecosystems
Springer, 2011
doi web bib

@book{PUB00033183, author = {Calabrese, J.M. and Deffuant, G. and Grimm, V.}, author = {Deffuant, G. and Gilbert, N.}, title = {Bridging the gap between computational models and viability based resilience in Savanna ecosystems}, bookTitle = {}, series = {Understanding complex systems}, publisher = {Springer}, pages = {107-130}, url = {http://cemadoc.irstea.fr/cemoa/PUB00033183}, doi = {http://dx.doi.org/10.1007/978-3-642-20423-4}, year = {2011}, affiliation = {SMITHSONIAN CONSERVATION BIOLOGY INSTITUTE FRONT ROYAL VA USA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; UFZ HELMHOLTZ CENTRE FOR ENVIRONMENTAL RESEARCH LEIPZIG DEU}, ISBNISSN = {ISBN-13: 978-3642204227}, abstract = {}, }
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X. Castello, F. Vazquez, V.M. Eguiluz, L. Loureiro-Porto, M. San Miguel, L. Chapel, G. Deffuant
Viability and resilience in the dynamics of language competition
Springer, 2011
doi web bib

@book{PUB00033181, author = {Castello, X. and Vazquez ,F. and Eguiluz, V.M. and Loureiro-Porto, L. and San Miguel, M. and Chapel, L. and Deffuant, G.}, author = {Deffuant, G. and Gilbert, N.}, title = {Viability and resilience in the dynamics of language competition}, bookTitle = {}, series = {Understanding complex systems}, publisher = {Springer}, pages = {39-73}, url = {http://cemadoc.irstea.fr/cemoa/PUB00033181}, doi = {http://dx.doi.org/10.1007/978-3-642-20423-4}, year = {2011}, affiliation = {IFISC UNIVERSITAT ILLES BALEARS PALMA DE MALLORCA ESP ; MPI PKS MAX PLANK INSTITUTE FOR THE PHYSICS OF COMPLEX SYSTEMS DRESDEN DEU ; IFISC UNIVERSITAT ILLES BALEARS PALMA DE MALLOCA ESP ; DEPARTMENT OF SPANISH MODERN LANGUAGES AND LATIN UNIVERSITAT ILLES BALEARS ESP ; IFISC UNIVERSITAT ILLES BALEARS PALMA DE MALLOCA ESP ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, ISBNISSN = {ISBN-13: 978-3642204227}, abstract = {}, }
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L. Chapel, G. Deffuant
Approximating viability kernels and resilience values: algorithms and practical issues illustrated with KAVIAR software
Springer, 2011
doi web bib

@book{PUB00033188, author = {Chapel, L. and Deffuant, G.}, author = {Deffuant, G. and Gilbert, N.}, title = {Approximating viability kernels and resilience values: algorithms and practical issues illustrated with KAVIAR software}, bookTitle = {}, series = {Understanding complex systems}, publisher = {Springer}, pages = {161-192}, url = {http://cemadoc.irstea.fr/cemoa/PUB00033188}, doi = {http://dx.doi.org/10.1007/978-3-642-20423-4}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, ISBNISSN = {ISBN-13: 978-3642204227}, abstract = {}, }
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G. Deffuant, N. Gilbert
Viability and resilience of complex systems: concepts, methods and case studies from ecology and society
Springer, 2011
abs doi web bib

One common characteristic of a complex system is its ability to withstand major disturbances and the capacity to rebuild itself. Understanding how such systems demonstrate resilience by absorbing or recovering from major external perturbations requires both quantitative foundations and a multidisciplinary view of the topic. This book demonstrates how new methods can be used to identify the actions favouring the recovery from perturbations on a variety of examples including the dynamics of bacterial biofilms, grassland savannahs, language competition and Internet social networking sites. The reader is taken through an introduction to the idea of resilience and viability and shown the mathematical basis of the techniques used to analyse systems. The idea of individual or agent-based modelling of complex systems is introduced and related to analytically tractable approximations of such models. A set of case studies illustrates the use of the techniques in real applications, and the final section describes how one can use new software tools for carrying out the necessary calculations. The book is intended for a general scientific audience of readers from the natural and social sciences, although it requires some mathematics to gain a full understanding of the more theoretical chapters. It is an essential point of reference for those interested in the practical application of the concepts of resilience and viability.
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@book{PUB00033170, author = {Deffuant, G. and Gilbert, N.}, title = {Viability and resilience of complex systems: concepts, methods and case studies from ecology and society}, series = {Understanding complex systems}, publisher = {Springer}, pages = {233}, url = {http://cemadoc.irstea.fr/cemoa/PUB00033170}, doi = {http://dx.doi.org/10.1007/978-3-642-20423-4}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; UNIVERSITY OF SURREY CENTRE FOR RESEARCH IN SOCIAL SIMULATION GUILFORD GBR}, ISBNISSN = {ISBN-13: 978-3642204227}, abstract = {One common characteristic of a complex system is its ability to withstand major disturbances and the capacity to rebuild itself. Understanding how such systems demonstrate resilience by absorbing or recovering from major external perturbations requires both quantitative foundations and a multidisciplinary view of the topic. This book demonstrates how new methods can be used to identify the actions favouring the recovery from perturbations on a variety of examples including the dynamics of bacterial biofilms, grassland savannahs, language competition and Internet social networking sites. The reader is taken through an introduction to the idea of resilience and viability and shown the mathematical basis of the techniques used to analyse systems. The idea of individual or agent-based modelling of complex systems is introduced and related to analytically tractable approximations of such models. A set of case studies illustrates the use of the techniques in real applications, and the final section describes how one can use new software tools for carrying out the necessary calculations. The book is intended for a general scientific audience of readers from the natural and social sciences, although it requires some mathematics to gain a full understanding of the more theoretical chapters. It is an essential point of reference for those interested in the practical application of the concepts of resilience and viability.}, }
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N. Mabrouk, J.D. Mathias, G. Deffuant
Viability and resilience of a bacterial biofilm individual-based model
Springer, 2011
doi web bib

@book{PUB00033187, author = {Mabrouk, N. and Mathias, J.D. and Deffuant, G.}, author = {Deffuant, G. and Gilbert, N.}, title = {Viability and resilience of a bacterial biofilm individual-based model}, bookTitle = {}, series = {Understanding complex systems}, publisher = {Springer}, pages = {131-157}, url = {http://cemadoc.irstea.fr/cemoa/PUB00033187}, doi = {http://dx.doi.org/10.1007/978-3-642-20423-4}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, ISBNISSN = {ISBN-13: 978-3642204227}, abstract = {}, }
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S. Martin, G. Deffuant, J.M. Calabrese
Defining resilience mathematically: from attractors to viability
Springer, 2011
doi web bib

@book{PUB00033173, author = {Martin, S. and Deffuant, G. and Calabrese, J.M.}, author = {Deffuant, G. and Gilbert, N.}, title = {Defining resilience mathematically: from attractors to viability}, bookTitle = {}, series = {Understanding complex systems}, publisher = {Springer}, pages = {15-36}, url = {http://cemadoc.irstea.fr/cemoa/PUB00033173}, doi = {http://dx.doi.org/10.1007/978-3-642-20423-4}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; UFZ HELMHOLTZ CENTRE FOR ENVIRONMENTAL RESEARCH LEIPZIG DEU}, ISBNISSN = {ISBN-13: 978-3642204227}, abstract = {}, }
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G. Deffuant
The empathon: Towards a computational agent mimicking empathy
Presses Universitaires Blaise Pascal, Clermont-Ferrand, 2010
abs web bib

This paper investigates a basic model simulating empathy. The model is abstracted from recent advances in neurobiology, such as the discovery of mirror neurons or of neurons coding for both visual recognition and connected action plans. In a very simplified computational environment, we define agents which associate action plans with visual stimuli, and are also able to feel such action plans when they observe another agent in a similar situation. We propose a first set of experiments involving only a pair of agents, with different action abilities.
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@book{PUB00030679, author = {Deffuant, G.}, author = {Hill, D.R.C. and Muzy, A. and Zeigler B.P. }, title = {The empathon: Towards a computational agent mimicking empathy }, bookTitle = {}, address = {Clermont-Ferrand}, publisher = {Presses Universitaires Blaise Pascal}, pages = {37-51}, url = {http://www.msh-clermont.fr/IMG/pdf/03-DEFFUANT_37-51_.pdf}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00030679}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {This paper investigates a basic model simulating empathy. The model is abstracted from recent advances in neurobiology, such as the discovery of mirror neurons or of neurons coding for both visual recognition and connected action plans. In a very simplified computational environment, we define agents which associate action plans with visual stimuli, and are also able to feel such action plans when they observe another agent in a similar situation. We propose a first set of experiments involving only a pair of agents, with different action abilities.}, }
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G. Deffuant, G. Weisbuch
Probability distribution dynamics explaining agent model convergence to extremism
Information Science Reference, Hershey, USA, 2008
abs web bib

This chapter studies continuous opinion models with extremists, and we use probability distribution models which approximate the behaviour of agents based models in order to explain their attractor patterns. The probability distribution is defined on a discrete grid in the opinion / uncertainty space. We compute the equations of probability flows between each couple of sites of the grid for different variants of the opinion influence model (bounded confidence, relative agreement and two others). The simulations show that the probability distribution models yield attractor patterns very similar to those obtained with the agent based models. Moreover, a study of the probability distribution evolution helps to better understand the process of convergence to single and double extreme attractors observed in agent based models.
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@book{PUB00025788, author = {Deffuant, G. and Weisbuch, G.}, author = {Edmonds, B. and Hernandez, C. and Troitzsch, K.}, title = {Probability distribution dynamics explaining agent model convergence to extremism}, title = {Des modèles d'évolution de distribution de probabilité pour expliquer la convergence vers l'extrémisme de modèles individus-centrés}, bookTitle = {}, address = {Hershey, USA}, publisher = {Information Science Reference}, pages = {43-60}, url = {http://cemadoc.irstea.fr/cemoa/PUB00025788}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; ENS ECOLE NORMALE SUPERIEURE PARIS LABORATOIRE DE PHYSIQUE STATISTQUE FRA}, ISBNISSN = {ISBN 978-1-59904-522-1}, abstract = {This chapter studies continuous opinion models with extremists, and we use probability distribution models which approximate the behaviour of agents based models in order to explain their attractor patterns. The probability distribution is defined on a discrete grid in the opinion / uncertainty space. We compute the equations of probability flows between each couple of sites of the grid for different variants of the opinion influence model (bounded confidence, relative agreement and two others). The simulations show that the probability distribution models yield attractor patterns very similar to those obtained with the agent based models. Moreover, a study of the probability distribution evolution helps to better understand the process of convergence to single and double extreme attractors observed in agent based models.}, }
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G. Deffuant, S. Huet, S. Skerratt
An agent based model of agri-environmental measure diffusion: What for ?
INSISOC, Valladolid, ESP, 2008
abs web bib

This paper focuses on the agent based model of the diffusion of agri-environmental measures developed in the IMAGES European project (1997 2001). We describe the main stages of this model elaboration, showing that it synthesises different modelling points of view. We then illustrate its representative power using a case study in Scotland. Finally, we point out some difficulties in the practical use of such models, particularly as decision supports for policy makers. We advocate a more careful study of the model through systematic experiments, and for the further development of a model of its aggregated dynamics, in order to give more reliable information to policy makers.
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@book{PUB00024125, author = {Deffuant, G. and Huet, S. and Skerratt, S.}, author = {Lopez Paredes, A. and Hernandez Iglesias, C.}, title = {An agent based model of agri-environmental measure diffusion: What for ?}, title = {Un modèle agent de diffusion de mesures agri-environnementales: pourquoi ?}, bookTitle = {}, address = {Valladolid, ESP}, publisher = {INSISOC}, pages = {55-73}, url = {http://cemadoc.irstea.fr/cemoa/PUB00024125}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; SCOTTISH AGRICULTURAL COLLEGE EDINBURGH GBR}, ISBNISSN = {ISBN 978-84-205-4560-8}, abstract = {This paper focuses on the agent based model of the diffusion of agri-environmental measures developed in the IMAGES European project (1997 2001). We describe the main stages of this model elaboration, showing that it synthesises different modelling points of view. We then illustrate its representative power using a case study in Scotland. Finally, we point out some difficulties in the practical use of such models, particularly as decision supports for policy makers. We advocate a more careful study of the model through systematic experiments, and for the further development of a model of its aggregated dynamics, in order to give more reliable information to policy makers. }, }
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In Collections (1)

G. Deffuant, F. Amblard, S. Huet, S. Bernard, N. Ferrand, J.P. Bousset, G. Amon, J. Henriot, N. Gilbert, E. Chattoe, G. Weisbuch
Simulation de l'évolution des conversions à l'agriculture biologique dans le département de l'Allier entre 1994 et 1999 par un modèle multi-agents department
2002
abs web bib

We present a model allowing to simulate the evolution of the conversions to organic farming in Allier department from 1994 to 1999. The model is made up of investigations carried out in the field as well as various statistical data. It is based on a statistically valid reconstruction of farmers of the department and their situation per district. The social networks of farmers (made up with other farmers and institutional actors) are considered in the model. The conversion decision is modelled like the result of a process including several stages. Social interactions and economic calculations closely mixed in this process. The aim in the long term is to provide prospective trends on the future evolutions of conversions, according to assumptions on the economic and political context. / Nous présentons un modèle permettant de simuler l'évolution des conversions à l'agriculture biologique dans le département de l'Allier entre 1994 et 1999. Le modèle se nourrit d'enquêtes réalisées sur le terrain ainsi que de données statistiques diverses. Il se fonde sur une reconstitution valide statistiquement de la population d'agriculteurs du département et leur localisation par commune. Les réseaux sociaux des agriculteurs (constitués d'autres agriculteurs et d'acteurs institutionnels) sont considérés dans le modèle. La décision de conversion est modélisée comme le résultat d'un processus comprenant plusieurs étapes. Interactions sociales et calculs économiques se mêlent étroitement dans ce processus. L'objectif du modèle à terme est de fournir des tendances prospectives sur les évolutions futures des conversions, en fonction d'hypothèses sur l'évolution du contexte économique et politique.
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@incollection{PUB00013158, author = {Deffuant, G. and Amblard, F. and Huet, S. and Bernard, S. and Ferrand, N. and Bousset, J.P. and Amon, G. and Henriot, J. and Gilbert, N. and Chattoe, E. and Weisbuch, G.}, title = {Simulation de l'évolution des conversions à l'agriculture biologique dans le département de l'Allier entre 1994 et 1999 par un modèle multi-agents department}, title = {Agent-based simulation of organic farming conversion in Allier }, bookTitle = {}, pages = {19}, url = {http://cemadoc.irstea.fr/cemoa/PUB00013158}, year = {2002}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND DFCF ; UNIVERSITY OF SURREY GUILDBORD GBR ; UNIVERSITY OF OXFORD GBR ; ECOLE NORMALE SUPERIEURE PARIS ; - ; - ; - ; - ; - ; -}, number = {02/0948 ; K LI02 8}, abstract = {We present a model allowing to simulate the evolution of the conversions to organic farming in Allier department from 1994 to 1999. The model is made up of investigations carried out in the field as well as various statistical data. It is based on a statistically valid reconstruction of farmers of the department and their situation per district. The social networks of farmers (made up with other farmers and institutional actors) are considered in the model. The conversion decision is modelled like the result of a process including several stages. Social interactions and economic calculations closely mixed in this process. The aim in the long term is to provide prospective trends on the future evolutions of conversions, according to assumptions on the economic and political context. / Nous présentons un modèle permettant de simuler l'évolution des conversions à l'agriculture biologique dans le département de l'Allier entre 1994 et 1999. Le modèle se nourrit d'enquêtes réalisées sur le terrain ainsi que de données statistiques diverses. Il se fonde sur une reconstitution valide statistiquement de la population d'agriculteurs du département et leur localisation par commune. Les réseaux sociaux des agriculteurs (constitués d'autres agriculteurs et d'acteurs institutionnels) sont considérés dans le modèle. La décision de conversion est modélisée comme le résultat d'un processus comprenant plusieurs étapes. Interactions sociales et calculs économiques se mêlent étroitement dans ce processus. L'objectif du modèle à terme est de fournir des tendances prospectives sur les évolutions futures des conversions, en fonction d'hypothèses sur l'évolution du contexte économique et politique.}, }
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In Proceedings (59)

L. Chapel, G. Deffuant
Inner and outer capture basin approximation with support vector machines
8th International Conference on Informatics in Control, Automation and Robotics, ICINCO 2011, 28/07/2011-31/07/2011, Noordwirjkerhout, NLD (p. 6), 2011
abs web bib

We propose a new approach to solve target hitting problems, that iteratively approximates capture basins at successive times, using a machine learning algorithm (as a particular case, we use Support Vector Machines) trained on points of a grid with boolean labels. We consider two variants of the approximation (from inside and from outside), and we state the conditions on the machine learning procedure that guarantee that the approximations converge to the actual capture basin when the resolution of the grid decreases to 0. Moreover, we define a control procedure which uses the set of capture basin approximations to drive a point into the target. When using the inner approximation, the procedure guarantees to hit the target, and when the resolution of the grid tends to 0, the controller tends to the optimal one (minimizing time to hit the target). SVMs provide parcimonious approximations, used to derive fast controllers. We illustrate the method on two simple examples, Zermelo and car on the hill problems.
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@inproceedings{PUB00034525, author = {Chapel, L. and Deffuant, G.}, title = {Inner and outer capture basin approximation with support vector machines}, title = {Approximation par l'intérieur et par l'extérieur de bassin de capture en utilisant des séparateurs à vaste marge}, bookTitle = {8th International Conference on Informatics in Control, Automation and Robotics, ICINCO 2011, 28/07/2011-31/07/2011, Noordwirjkerhout, NLD}, pages = {6}, url = {http://cemadoc.irstea.fr/cemoa/PUB00034525}, year = {2011}, affiliation = {UNVIERSITE DE BRETAGNE SUD LAB STICC VANNES FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {We propose a new approach to solve target hitting problems, that iteratively approximates capture basins at successive times, using a machine learning algorithm (as a particular case, we use Support Vector Machines) trained on points of a grid with boolean labels. We consider two variants of the approximation (from inside and from outside), and we state the conditions on the machine learning procedure that guarantee that the approximations converge to the actual capture basin when the resolution of the grid decreases to 0. Moreover, we define a control procedure which uses the set of capture basin approximations to drive a point into the target. When using the inner approximation, the procedure guarantees to hit the target, and when the resolution of the grid tends to 0, the controller tends to the optimal one (minimizing time to hit the target). SVMs provide parcimonious approximations, used to derive fast controllers. We illustrate the method on two simple examples, Zermelo and car on the hill problems.}, }
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B. Gandar, G. Loosli, G. Deffuant
Dispersion effect on generalisation error in classification: Experimental proof and practical algorithm
ICAART 2011 Conference .3rd Congference on Agents and Artificial Intelligence, 28/01/2011-30/01/2011, Rome, ITA (p. 4), 2011
abs web bib

Recent theoretical work proposes criteria of dispersion to generate learning points. The aim of this paper is to convince the reader, with experimental proofs, that dispersion is a good criterion in practice for generating learning points for classification problems. Problem of generating learning points consists then in generating points with the lowest dispersion. As a consequence, we present low dispersion algorithms existing in the literature, analyze them and propose a new algorithm.
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@inproceedings{PUB00034342, author = {Gandar, B. and Loosli, G. and Deffuant, G.}, title = {Dispersion effect on generalisation error in classification: Experimental proof and practical algorithm}, title = {Effet de la dispersion sur l'erreur en généralisation en classification : preuve expérimentale et algorithme pratique}, bookTitle = {ICAART 2011 Conference .3rd Congference on Agents and Artificial Intelligence, 28/01/2011-30/01/2011, Rome, ITA}, pages = {4}, url = {http://cemadoc.irstea.fr/cemoa/PUB00034342}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; UNIVERSITE CLERMONT LIMOS UMR 6158 FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {Recent theoretical work proposes criteria of dispersion to generate learning points. The aim of this paper is to convince the reader, with experimental proofs, that dispersion is a good criterion in practice for generating learning points for classification problems. Problem of generating learning points consists then in generating points with the lowest dispersion. As a consequence, we present low dispersion algorithms existing in the literature, analyze them and propose a new algorithm.}, }
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S. Huet, M. Lenormand, G. Deffuant
Modelling a network of rural municipalities
ESSA 2011, 19/09/2011-23/09/2011, Montpellier, FRA , 2011
abs web bib

The poster describes the dynamics of individuals changing activities and status on the labour market in a large individual-based model simulating the rural municipalities. Some results are presented for seven municipalities of the French Cantal department. / Ce poster décrit la dynamique d'activité des individus du modèle PRIMA dédié à la modélisation des municipalités rurales.
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@inproceedings{PUB00033512, author = {Huet,S. and Lenormand,M. and Deffuant,G.}, title = {Modelling a network of rural municipalities }, title = {La modélisation d'un réseau de municipalités rurales}, bookTitle = {ESSA 2011, 19/09/2011-23/09/2011, Montpellier, FRA}, url = {http://cemadoc.irstea.fr/cemoa/PUB00033512}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {The poster describes the dynamics of individuals changing activities and status on the labour market in a large individual-based model simulating the rural municipalities. Some results are presented for seven municipalities of the French Cantal department. / Ce poster décrit la dynamique d'activité des individus du modèle PRIMA dédié à la modélisation des municipalités rurales.}, }
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M. Lenormand, G. Deffuant, S. Huet
Calibrating a complex social model
European Conference on Complex Systems ECCS'11, 12/09/2011-16/09/2011, Vienne, AUT , 2011
abs web bib

Approximate Bayesian computation is a family of computational techniques in Bayesian statistics. These techniques allow to fit a model to data without relying on the computation of the model likelihood. A number of improvements to the original ABC scheme have been proposed to speed it up. They include the coupling to Markov chain Monte Carlo to explore the parameter space and the sequential improvement of posterior distributions inspired by sequential Monte Carlo methods. These algorithms present severals shortcomings which are particularly problematic for costly to simulate complex models. In this article an adaptive appoximate Bayesian computation for complex models is proposed which offers improvements to circumvent the limitations of the application of the ABC methods to complex models. We demonstrate our algorithm on a toy example and on a complex social model, the PRIMA model.
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@inproceedings{PUB00033827, author = {Lenormand, M. and Deffuant, G. and Huet, S.}, title = {Calibrating a complex social model}, title = {Calibration d'un modèle social complexe}, bookTitle = {European Conference on Complex Systems ECCS'11, 12/09/2011-16/09/2011, Vienne, AUT}, url = {http://cemadoc.irstea.fr/cemoa/PUB00033827}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {Approximate Bayesian computation is a family of computational techniques in Bayesian statistics. These techniques allow to fit a model to data without relying on the computation of the model likelihood. A number of improvements to the original ABC scheme have been proposed to speed it up. They include the coupling to Markov chain Monte Carlo to explore the parameter space and the sequential improvement of posterior distributions inspired by sequential Monte Carlo methods. These algorithms present severals shortcomings which are particularly problematic for costly to simulate complex models. In this article an adaptive appoximate Bayesian computation for complex models is proposed which offers improvements to circumvent the limitations of the application of the ABC methods to complex models. We demonstrate our algorithm on a toy example and on a complex social model, the PRIMA model.}, }
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M. Lenormand, G. Deffuant, S. Huet
A commuting generation model requiring only aggregated data
7th European Social Simulation Association Conference, 19/09/2011-23/09/2011, Montpellier, FRA (p. 16), 2011
abs web bib

We recently proposed, in (Gargiulo et al., 2011), an innovative stochastic model with only one parameter to calibrate. It reproduces the complete network by an iterative process stochastically choosing, for each commuter living in the municipality of a region, a workplace in the region. The choice is done considering the job offer in each municipality of the region and the distance to all the possible destinations. The model is quite effective if the region is sufficiently autonomous in terms of job offers. However, calibrating or being sure of this autonomy require data or expertise which are not necessarily available. Moreover the region can be not autonomous. In the present, we overcome these limitations, extending the job search geographical base of the commuters to the outside of the region, and changing the deterrence function form. We also found a law to calibrate the improvement model which does not require data.
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@inproceedings{PUB00033826, author = {Lenormand, M. and Deffuant, G. and Huet, S.}, title = {A commuting generation model requiring only aggregated data}, title = {Un modèle de génération de réseau de navettage nécessitant uniquement des données agrégées}, bookTitle = {7th European Social Simulation Association Conference, 19/09/2011-23/09/2011, Montpellier, FRA}, pages = {16}, url = {http://cemadoc.irstea.fr/cemoa/PUB00033826}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {We recently proposed, in (Gargiulo et al., 2011), an innovative stochastic model with only one parameter to calibrate. It reproduces the complete network by an iterative process stochastically choosing, for each commuter living in the municipality of a region, a workplace in the region. The choice is done considering the job offer in each municipality of the region and the distance to all the possible destinations. The model is quite effective if the region is sufficiently autonomous in terms of job offers. However, calibrating or being sure of this autonomy require data or expertise which are not necessarily available. Moreover the region can be not autonomous. In the present, we overcome these limitations, extending the job search geographical base of the commuters to the outside of the region, and changing the deterrence function form. We also found a law to calibrate the improvement model which does not require data.}, }
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J.D. Mathias, F. Chuffart, N. Mabrouk, G. Deffuant
Applying a moment approximation to a bacterial biofilm individual-based model
4th International Multi-Conference on Computing in the Global Information Technology, ICCGI 2009 , 23/09/2009-29/09/2009, Nice, FRA (p. 138-143), 2011
abs web bib

We consider a 2D individual-based model of biofilm, in which bacteria can generate a polymeric substance (EPS), The coupling between polymer generation and bacteria creates a variety of biofilm structures. Then, we derive the equations of first and second moment evolution for the bacteria and EPS particle population sizes. This approximation of the dynamics is much lighter to compute than the whole IBM, hence more systematic exploration is easier particularly in case of large bacteria populations. We show that the second moment approximation predicts accurately the quantities of bacteria and polymer. Moreover, it gives relevant information about their spatial distribution.
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@inproceedings{PUB00033283, author = {Mathias, J.D. and Chuffart, F. and Mabrouk, N. and Deffuant, G.}, title = {Applying a moment approximation to a bacterial biofilm individual-based model}, bookTitle = {4th International Multi-Conference on Computing in the Global Information Technology, ICCGI 2009 , 23/09/2009-29/09/2009, Nice, FRA}, pages = {138-143}, url = {http://cemadoc.irstea.fr/cemoa/PUB00033283}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF AIX EN PROVENCE SGAX FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {We consider a 2D individual-based model of biofilm, in which bacteria can generate a polymeric substance (EPS), The coupling between polymer generation and bacteria creates a variety of biofilm structures. Then, we derive the equations of first and second moment evolution for the bacteria and EPS particle population sizes. This approximation of the dynamics is much lighter to compute than the whole IBM, hence more systematic exploration is easier particularly in case of large bacteria populations. We show that the second moment approximation predicts accurately the quantities of bacteria and polymer. Moreover, it gives relevant information about their spatial distribution. }, }
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B. Gandar, G. Loosli, G. Deffuant
How to generate the best low dispersion samples for active learning in classification ?
Active Learning and Experimental Design Workshop AISTATS, 16/05/2010, Sardaigne, FRA (p. 16), 2010
abs web bib

We consider a problem of active learning classification: we suppose we can determine, with an oracle, the label of any point in a given compact set, and we want to generate a sample of a given size which will allow us to get the best approximation of the oracle function. It's well known that the more numerous the data are, the best quality the modelling is. However obtaining data can be expensive or destructive in consequence we want to get the best value from this investment. We have to choose the best learning set. The first contribution of this paper is to state that dispersion is the most relevant criterion for generating samples in active classification leanring whereas discrepance is the relevant criterion for active regression learning. However low dispersion samples are not easy to generate. The second contribution consists then in making a study of different ways to proceed and in proposing a new algorithm.
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@inproceedings{PUB00030736, author = {Gandar, B. and Loosli, G. and Deffuant, G.}, title = {How to generate the best low dispersion samples for active learning in classification ?}, title = {Comment générer les meilleurs échantillons a faible dispersion pour l'apprentissage actif en classification ?}, bookTitle = {Active Learning and Experimental Design Workshop AISTATS, 16/05/2010, Sardaigne, FRA}, pages = {16}, url = {http://cemadoc.irstea.fr/cemoa/PUB00030736}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; LIMOS UNIVERSITE BLAISE PASCAL CLERMONT FERRAND FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {We consider a problem of active learning classification: we suppose we can determine, with an oracle, the label of any point in a given compact set, and we want to generate a sample of a given size which will allow us to get the best approximation of the oracle function. It's well known that the more numerous the data are, the best quality the modelling is. However obtaining data can be expensive or destructive in consequence we want to get the best value from this investment. We have to choose the best learning set. The first contribution of this paper is to state that dispersion is the most relevant criterion for generating samples in active classification leanring whereas discrepance is the relevant criterion for active regression learning. However low dispersion samples are not easy to generate. The second contribution consists then in making a study of different ways to proceed and in proposing a new algorithm.}, }
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T. Guelon, J.D. Mathias, G. Deffuant
Homogenization of the diffusion of bacterial biofilms
IV European Conference on Computational Mechanics, ECCM2010, 16/05/2010-21/05/2010, Paris , 2010
web bib

@inproceedings{PUB00031628, author = {Guelon, T. and Mathias, J.D. and Deffuant, G.}, title = {Homogenization of the diffusion of bacterial biofilms}, title = {Homogénéisation de la diffusion dans les biofilms bactériens}, bookTitle = {IV European Conference on Computational Mechanics, ECCM2010, 16/05/2010-21/05/2010, Paris}, url = {http://cemadoc.irstea.fr/cemoa/PUB00031628}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {}, }
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T. Guelon, J.D. Mathias, G. Deffuant
Homogenization of physical properties of bacterial biofilms
CE2M10 (Changement d'échelle en mécanique des matériaux), 22/08/2010-03/09/2010, Briançon, FRA , 2010
web bib

@inproceedings{PUB00031627, author = {Guelon, T. and Mathias, J.D. and Deffuant, G.}, title = {Homogenization of physical properties of bacterial biofilms}, title = {Homogénéisation des propriétés physiques des biofilms bactériens}, bookTitle = {CE2M10 (Changement d'échelle en mécanique des matériaux), 22/08/2010-03/09/2010, Briançon, FRA}, url = {http://cemadoc.irstea.fr/cemoa/PUB00031627}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {}, }
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T. Guélon, J.D. Mathias, G. Deffuant
Applying a multiscale approach to explain biofilm formation
Advances in Interaction and Multiscale Mechanics" ( AIMM'10), 30/05/2010-03/06/2010, Jeju, KOR , 2010
abs web bib

In this paper, we study the structure of a biofilm using homogenization techniques, which have been developed to characterize heterogeneous materials in physics. The properties of the biofilm depend therefore on the considered scale where they are calculated. Homogenization techniques are then applied on biofilm in order to determine emergent properties. We especially focus on the nutrient access properties and the link with biofilm structure.
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@inproceedings{PUB00031626, author = {Guélon, T. and Mathias, J.D. and Deffuant, G.}, title = {Applying a multiscale approach to explain biofilm formation}, title = {Application d'une approche multi-échelle pour expliquer la formation des biofilms}, bookTitle = {Advances in Interaction and Multiscale Mechanics" ( AIMM'10), 30/05/2010-03/06/2010, Jeju, KOR}, url = {http://cemadoc.irstea.fr/cemoa/PUB00031626}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {In this paper, we study the structure of a biofilm using homogenization techniques, which have been developed to characterize heterogeneous materials in physics. The properties of the biofilm depend therefore on the considered scale where they are calculated. Homogenization techniques are then applied on biofilm in order to determine emergent properties. We especially focus on the nutrient access properties and the link with biofilm structure.}, }
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T. Guélon, J.D. Mathias, R.C. Hunter, G. Deffuant
Applying homogenization techniques to determine macroscopic mechanical properties of bacterial biofilms
Biofilms4 International Conference , 01/09/2010-03/09/2010, Winchester, UK, GBR (p. 1), 2010
web bib

@inproceedings{PUB00031563, author = {Guélon, T. and Mathias, J.D. and Hunter, R.C. and Deffuant, G.}, title = {Applying homogenization techniques to determine macroscopic mechanical properties of bacterial biofilms}, title = {Utilisation des techniques d'homogénéisation pour déterminer les propriétés mécaniques macroscopiques des biofilms bactériens}, bookTitle = {Biofilms4 International Conference , 01/09/2010-03/09/2010, Winchester, UK, GBR}, pages = {1}, url = {http://cemadoc.irstea.fr/cemoa/PUB00031563}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CALIFORNIA INSTITUTE OF TECHNOLOGY PASADENA DIVISION OF BIOLOGY USA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {}, }
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N. Mabrouk, J.D. Mathias, G. Deffuant
Computing the resilience of a wastewater treatment bioreactor
5th International Multi-Conference on Computing in the Global Information Technology, ICCGI 2010, 20/09/2010-25/09/2010, Valencia, ESP (p. 185-188), 2010
abs pdf doi bib

Biological wastewater treatment reactor are designed to reduce the pollutant content of a wastewater to an acceptable level often fixed by wastewater discharge regulations. The reactor design is often based on average wastewater flow and composition patterns. However, industrial wastewater treatment reactors are often subject to unexpected perturbations (variations in wastewater flow, composition or shift in the microbial communities). Hence the capacity of the reactor to recover from these perturbations in reasonable times should also be considered as an important design criteria. In this work we illustrate how this property can be quantified by calculating reactor resilience using return time concept. We show that a reactor design that maximizes the productivity (in term of mass of pollutant removed per unit of time and unit of reactor volume) may not be optimal in term of resilience. Hence, a compromise between productivity and resilience should be targeted when designing biological wastewater treatment reactors.
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@inproceedings{PUB00032277, author = {Mabrouk, N. and Mathias, J.D. and Deffuant, G.}, title = {Computing the resilience of a wastewater treatment bioreactor}, bookTitle = {5th International Multi-Conference on Computing in the Global Information Technology, ICCGI 2010, 20/09/2010-25/09/2010, Valencia, ESP}, pages = {185-188}, pdf = {http://motive.cemagref.fr/_publication/PUB00032277.pdf}, doi = {http://dx.doi.org/10.1109/ICCGI.2010.60}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, ISBNISSN = {ISBN 978-076954181-5}, abstract = {Biological wastewater treatment reactor are designed to reduce the pollutant content of a wastewater to an acceptable level often fixed by wastewater discharge regulations. The reactor design is often based on average wastewater flow and composition patterns. However, industrial wastewater treatment reactors are often subject to unexpected perturbations (variations in wastewater flow, composition or shift in the microbial communities). Hence the capacity of the reactor to recover from these perturbations in reasonable times should also be considered as an important design criteria. In this work we illustrate how this property can be quantified by calculating reactor resilience using return time concept. We show that a reactor design that maximizes the productivity (in term of mass of pollutant removed per unit of time and unit of reactor volume) may not be optimal in term of resilience. Hence, a compromise between productivity and resilience should be targeted when designing biological wastewater treatment reactors.}, }
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K. Takadama, C. Cioffi-Revilla, G. Deffuant
Simulating interacting agents and social phenomena
The second world Congress on Social Simulation (WCSS'08), 14/07/2008-17/07/2008, Fairfax, Virginia, USA , Springer, 2010
doi web bib

@inproceedings{PUB00031372, author = {Takadama, K. and Cioffi-Revilla, C. and Deffuant, G.}, title = {Simulating interacting agents and social phenomena}, bookTitle = {The second world Congress on Social Simulation (WCSS'08), 14/07/2008-17/07/2008, Fairfax, Virginia, USA}, series = {ABSS - Agent-based social systems vol. 7}, publisher = {Springer}, url = {http://cemadoc.irstea.fr/cemoa/PUB00031372}, doi = {http://dx.doi.org/10.1007/978-4-431-99781-8}, year = {2010}, affiliation = {DEPARTMENT OF INFORMATICS AND ENGINEERING UNIVERSITY OF ELECTRO6COMMUNICATIONS CHOFU JPN ; CENTER FOR SOCIAL COMPLEXITY GEORGE MASON UNIVERSITY FAIRFAX USA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, ISBNISSN = {ISBN 978-4-431-99780-1}, abstract = {}, }
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B. Gandar, G. Loosli, G. Deffuant
Sélection de points en apprentissage actif. Discrépance et dispersion : des critères optimaux ?
MajecSTIC 2009 , 16/11/2009-18/11/2009, Avignon, FRA (p. 8), 2009
abs pdf bib

Nous souhaitons générer des bases d'apprentissage adaptées aux problèmes de classification. Nous montrons tout d'abord que les résultats théoriques privilégiant les suites à discrépance faible pour les problèmes de régression sont inadaptés aux problèmes de classification. Nous donnons ensuite des arguments théoriques et des résultats de simulations montrant que c'est la dispersion des points d'apprentissage qui est le critère pertinent à minimiser pour optimiser les performances de l'apprentissage en classification.
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@inproceedings{PUB00027310, author = {Gandar, B. and Loosli, G. and Deffuant, G.}, title = {Sélection de points en apprentissage actif. Discrépance et dispersion : des critères optimaux ?}, title = {Selection of points in active learning. Discrepancy and dispersion: optimal criterion ? }, bookTitle = {MajecSTIC 2009 , 16/11/2009-18/11/2009, Avignon, FRA}, pages = {8}, pdf = {http://motive.cemagref.fr/_publication/PUB00027310.pdf}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; UNIVERSITE BLAISE PASCAL LIMOS CLERMONT FERRAND FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {Nous souhaitons générer des bases d'apprentissage adaptées aux problèmes de classification. Nous montrons tout d'abord que les résultats théoriques privilégiant les suites à discrépance faible pour les problèmes de régression sont inadaptés aux problèmes de classification. Nous donnons ensuite des arguments théoriques et des résultats de simulations montrant que c'est la dispersion des points d'apprentissage qui est le critère pertinent à minimiser pour optimiser les performances de l'apprentissage en classification.}, }
close
B. Gandar, G. Loosli, G. Deffuant
Discrépance et dispersion : des indicateurs optimaux pour approcher des surfaces de réponse par des SVMs ?
Journée du GdR MASCOT-NUM (Groupement de recherche Méthodes d'Analyse Stochastique des Codes et Traitements Numériques), 18/03/2009-18/03/2009, Saint Denis, FRA (p. 1), 2009
abs web bib

--
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@inproceedings{PUB00027309, author = {Gandar, B. and Loosli, G. and Deffuant, G.}, title = {Discrépance et dispersion : des indicateurs optimaux pour approcher des surfaces de réponse par des SVMs ?}, title = {Discrepancy and dispersion : optimal indicator to approach answer reponse with SVMs?}, bookTitle = {Journée du GdR MASCOT-NUM (Groupement de recherche Méthodes d'Analyse Stochastique des Codes et Traitements Numériques), 18/03/2009-18/03/2009, Saint Denis, FRA}, pages = {1}, url = {http://www.gdr-mascotnum.fr/}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00027309}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; UNIVERSITE BLAISE PASCAL CLERMONT FERRAND II LIMOS FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {--}, }
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B. Gandar, G. Loosli, G. Deffuant
How to optimize sample in active learning: Dispersion, an optimum criterion for classification ?
ENBIS (European Network for Business and Industrial Statistics) , 01/07/2009-03/07/2009, Saint-Etienne, FRA , 2009
abs web bib

We want generate learning data appropriated to classification problems. First, we show that theorical results about low discrepancy sequences in regression problems are not adequate for classification problems. Then, we show with theorical and experimental arguments that minimising the dispersion of the sample is a relevant strategy to optimize performance of classification learning.
close

@inproceedings{PUB00026365, author = {Gandar, B. and Loosli, G. and Deffuant, G.}, title = {How to optimize sample in active learning: Dispersion, an optimum criterion for classification ?}, title = {Comment optimiser les exemples en apprentissage actif : la dispersion, un critère optimal en classification ? }, bookTitle = {ENBIS (European Network for Business and Industrial Statistics) , 01/07/2009-03/07/2009, Saint-Etienne, FRA}, url = {http://cemadoc.irstea.fr/cemoa/PUB00026365}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; UNIVERSITE CLERMONT FERRAND FRA LIMOS ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {We want generate learning data appropriated to classification problems. First, we show that theorical results about low discrepancy sequences in regression problems are not adequate for classification problems. Then, we show with theorical and experimental arguments that minimising the dispersion of the sample is a relevant strategy to optimize performance of classification learning.}, }
close
B. Gandar, G. Loosli, G. Deffuant
Discrépance et dispersion : des critères optimaux en apprentissage ?
CAP'09 (Conférence en Apprentissage), 25/05/2009-29/05/2009, Hammamet, TUN (p. 4), 2009
abs web bib

Nous souhaitons générer des bases d'apprentissage adaptées à la classification. Nous montrons d'abord que les résultats théoriques privilégiant les suites à discrépance faible pour les problèmes de régression sont inadaptés à la classification. Puis nous donnons des arguments théoriques et des résultats de simulation montrant que c'est la dispersion des points d'apprentissage qui est le critère pertinent à minimiser pour optimiser les performances en classification.
close

@inproceedings{PUB00026366, author = {Gandar, B. and Loosli, G. and Deffuant, G.}, title = {Discrépance et dispersion : des critères optimaux en apprentissage ?}, title = {Discrepance and dispersion : optimum criterion in machine learning ? }, bookTitle = {CAP'09 (Conférence en Apprentissage), 25/05/2009-29/05/2009, Hammamet, TUN}, pages = {4}, url = {http://cemadoc.irstea.fr/cemoa/PUB00026366}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CNRS LIMOS UMR 6158 AUBIERE ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {Nous souhaitons générer des bases d'apprentissage adaptées à la classification. Nous montrons d'abord que les résultats théoriques privilégiant les suites à discrépance faible pour les problèmes de régression sont inadaptés à la classification. Puis nous donnons des arguments théoriques et des résultats de simulation montrant que c'est la dispersion des points d'apprentissage qui est le critère pertinent à minimiser pour optimiser les performances en classification.}, }
close
S. Huet, G. Deffuant
De l'importance des individus moins engagés pour l'émergence d'une majorité
MASHS : Modèles et Apprentissage en Sciences Humaines et Sociales, 08/06/2009-09/06/2009, Toulouse, FRA (p. 12), 2009
abs web bib

Nous avons proposé un nouveau modèle de dynamique d'opinions basé sur les expériences et les résultats de Wood et al (1996). Un individu a plusieurs attitudes, chacune dotée d'une importance. L'importance de chaque attitude et la distance à un interlocuteur sur chacune des attitudes permet à l'individu de déterminer s'il juge la position de son interlocuteur positivement, négativement ou s'il y est indifférent. Lorsqu'il juge sa position positive, l'individu se rapproche de son interlocuteur sur toutes les dimensions attitudinales. Lorsqu'il la juge négativement, il s'éloigne sur les dimensions où il était proche. Une indifférence n'entraîne aucun changement d'attitude. Le modèle souligne d'une part l'importance de l'existence d'individus ne considérant pas une dimension plus importante que l'autre. Ces individus permettent l'émergence d'une majorité. Il montre également qu'en absence de tels individus, la population s'organise en petits groupes de taille homogène. Elle parvient à cet état en se rapprochant tout d'abord autour des questions peu importantes. Ce rapprochement rend saillant les divergences sur les questions importantes et incite les individus à s'organiser en petits groupes se repoussant et s'attirant en même temps.
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@inproceedings{PUB00026805, author = {Huet, S. and Deffuant, G.}, title = {De l'importance des individus moins engagés pour l'émergence d'une majorité}, title = {Less involved people are very important for a majority emergence}, bookTitle = {MASHS : Modèles et Apprentissage en Sciences Humaines et Sociales, 08/06/2009-09/06/2009, Toulouse, FRA}, pages = {12}, url = {http://cemadoc.irstea.fr/cemoa/PUB00026805}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {Nous avons proposé un nouveau modèle de dynamique d'opinions basé sur les expériences et les résultats de Wood et al (1996). Un individu a plusieurs attitudes, chacune dotée d'une importance. L'importance de chaque attitude et la distance à un interlocuteur sur chacune des attitudes permet à l'individu de déterminer s'il juge la position de son interlocuteur positivement, négativement ou s'il y est indifférent. Lorsqu'il juge sa position positive, l'individu se rapproche de son interlocuteur sur toutes les dimensions attitudinales. Lorsqu'il la juge négativement, il s'éloigne sur les dimensions où il était proche. Une indifférence n'entraîne aucun changement d'attitude. Le modèle souligne d'une part l'importance de l'existence d'individus ne considérant pas une dimension plus importante que l'autre. Ces individus permettent l'émergence d'une majorité. Il montre également qu'en absence de tels individus, la population s'organise en petits groupes de taille homogène. Elle parvient à cet état en se rapprochant tout d'abord autour des questions peu importantes. Ce rapprochement rend saillant les divergences sur les questions importantes et incite les individus à s'organiser en petits groupes se repoussant et s'attirant en même temps.}, }
close
S. Huet, G. Deffuant
Openness leads to Opinion Stability and Narrowness to Volatility
ECCS'09, European Conference on Complex Systems, 21/09/2009-25/09/2009, Warwick, GBR (p. 14), 2009
abs web bib

We propose a new opinion dynamic model based on the experiments and results of Wood et al (1996). We consider pairs of individuals discussing on two attitudinal dimensions, and we suppose that one dimension is important, the other secondary. The dynamics are mainly ruled by the level of agreement on the main dimension. If two individuals are close on the main dimension, then they attract each other on the main and on the secondary dimensions, whatever their disagreement on the secondary dimension. If they are far from each other on the main dimension, then too much proximity on the secondary dimension is uncomfortable, and generates rejection on this dimension. The proximity is defined by comparing the opinion distance with a threshold called attraction threshold on the main dimension and rejection threshold on the secondary dimension. With such dynamics, a population with opinions initially uniformly drawn evolves to a set of clusters, inside which secondary opinions fluctuate more or less depending on threshold values. We observe that a low attraction threshold favours fluctuations on the secondary dimension, especially when the rejection threshold is high. The trajectories of the model can be related to some stylised facts.
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@inproceedings{PUB00026801, author = {Huet, S. and Deffuant, G.}, title = {Openness leads to Opinion Stability and Narrowness to Volatility}, title = {L'ouverture d'esprit mène à la stabilité des opinions tandis que l'étroitesse les rend volatiles}, bookTitle = {ECCS'09, European Conference on Complex Systems, 21/09/2009-25/09/2009, Warwick, GBR}, pages = {14}, url = {http://cemadoc.irstea.fr/cemoa/PUB00026801}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {We propose a new opinion dynamic model based on the experiments and results of Wood et al (1996). We consider pairs of individuals discussing on two attitudinal dimensions, and we suppose that one dimension is important, the other secondary. The dynamics are mainly ruled by the level of agreement on the main dimension. If two individuals are close on the main dimension, then they attract each other on the main and on the secondary dimensions, whatever their disagreement on the secondary dimension. If they are far from each other on the main dimension, then too much proximity on the secondary dimension is uncomfortable, and generates rejection on this dimension. The proximity is defined by comparing the opinion distance with a threshold called attraction threshold on the main dimension and rejection threshold on the secondary dimension. With such dynamics, a population with opinions initially uniformly drawn evolves to a set of clusters, inside which secondary opinions fluctuate more or less depending on threshold values. We observe that a low attraction threshold favours fluctuations on the secondary dimension, especially when the rejection threshold is high. The trajectories of the model can be related to some stylised facts.}, }
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S. Ternès, F. Gargiulo, S. Huet, G. Deffuant
Double modelling of the dynamic of activities in rural municipalities
7th Brazilian Congress of Agro-informatics (7. Congresso Brasileiro de Agroinformática ), 21/09/2009-25/09/2009, Viçosa, BRA (p. 5), 2009
abs web bib

Land use choices and activity prevalence in a selected territory are determined by individual preferences constrained by the characteristic of the analysed zone: population density, soil properties, urbanization level and other similar factors can drive individuals to make different kind of decisions about their occupations. Different approaches can be used to describe land use change, occupation prevalence and their reciprocal inter-relation. In this paper we describe two different kinds of approaches: an agent based model, centred on individual choices and an aggregated model describing the evolution of activity prevalence in terms of coupled differential equation. We use and we compare the two models to analyse the effect of territorial constraints, like the lack of employment in determined sectors, on the possible activity prevalence scenarios.
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@inproceedings{PUB00026804, author = {Ternès, S. and Gargiulo, F. and Huet, S. and Deffuant, G.}, title = {Double modelling of the dynamic of activities in rural municipalities}, bookTitle = {7th Brazilian Congress of Agro-informatics (7. Congresso Brasileiro de Agroinformática ), 21/09/2009-25/09/2009, Viçosa, BRA}, pages = {5}, url = {http://cemadoc.irstea.fr/cemoa/PUB00026804}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {Land use choices and activity prevalence in a selected territory are determined by individual preferences constrained by the characteristic of the analysed zone: population density, soil properties, urbanization level and other similar factors can drive individuals to make different kind of decisions about their occupations. Different approaches can be used to describe land use change, occupation prevalence and their reciprocal inter-relation. In this paper we describe two different kinds of approaches: an agent based model, centred on individual choices and an aggregated model describing the evolution of activity prevalence in terms of coupled differential equation. We use and we compare the two models to analyse the effect of territorial constraints, like the lack of employment in determined sectors, on the possible activity prevalence scenarios.}, }
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N. Turpin, R. Laplana, D. Kopeva, L. Stapleton, K. Happe, G. Deffuant, F. Brouwer, M. Burghard
PRIMA, Prototypical Policy Impacts on Multi-functional Activities in rural municipalities
AgSAP Conference 2009, 10/03/2009-12/03/2009, Egmond aan Zee, NLD / Van Ittersum, M.K., Wolf J. and Van Laar H.H. (Eds), 2009, Proceedings of the conference on Integrated Assessment of Agriculture and sustainable Development: Setting the Agenda for Science and Policy (AgSAP 2009), Egmond aan Zee, the Netherlands, 10-12 mars 2009 (p. 64-65), Wageningen University and Research Center, Wageningen, NLD, 2009
abs web bib

Poster décrivant le projet Prima
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@inproceedings{PUB00026414, author = {Turpin, N. and Laplana, R. and Kopeva, D. and Stapleton, L. and Happe, K. and Deffuant, G. and Brouwer, F. and Burghard, M.}, title = {PRIMA, Prototypical Policy Impacts on Multi-functional Activities in rural municipalities}, bookTitle = {AgSAP Conference 2009, 10/03/2009-12/03/2009, Egmond aan Zee, NLD / Van Ittersum, M.K., Wolf J. and Van Laar H.H. (Eds), 2009, Proceedings of the conference on Integrated Assessment of Agriculture and sustainable Development: Setting the Agenda for Science and Policy (AgSAP 2009), Egmond aan Zee, the Netherlands, 10-12 mars 2009}, address = {Wageningen, NLD}, publisher = {Wageningen University and Research Center}, pages = {64-65}, url = {http://cemadoc.irstea.fr/cemoa/PUB00026414}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR MECF UMR METAFORT FRA ; CEMAGREF BORDEAUX UR ADBX FRA ; - ; UNIVERSITY OF SUSSEX GBR ; - ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; LEI WAGENINGEN NLD ; -}, ISBNISSN = {ISBN 978-90-8585-401-2}, abstract = {Poster décrivant le projet Prima}, }
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L. Chapel, G. Deffuant
Utiliser des machines à vecteurs de support pour approcher les contours d'une fonction valeur dans des problèmes d'atteinte de cible
12ème Journée Scientifique de l'Ecole Doctorale Sciences Pour l'Ingénieur Apprentisage Statistique Apprentissage Symbolique, 04/06/2008-04/06/2008, Clermont Ferrand, FRA (p. 10), 2008
abs web bib

Nous proposons d'utiliser un algorithme d'apprentissage particulier, les SVMs, pour résoudre des problèmes d'atteinte de cible en temps minimal. La cible correspond à un état souhaité, en sachant que le système se détériore dans une certaine région de l'espace (lorsqu'il transgresse un ensemble de contraintes de viabilité). Le bassin de capture au temps t correspond à l'ensemble des états qui peuvent atteindre la cible en un temps inférieur ou égal à t, sans quitter l'ensemble des contrainte de viabilité. Les frontières d'un bassin de capture au temps t correspondent alors aux contours d'une fonction valeur au temps t. Les bassins de capture peuvent alors être utilisés pour définir une fonction de contrôle qui permet au système d'atteindre la cible en un temps minimal. Nous proposons une nouvelle approche, basée sur les SVMs, qui permet d'approcher les bassins de capture successifs et définissons une procédure de contrôle qui permet de contrôler le système afin qu'il atteigne la cible. Nous illustrons cette méthode sur un exemple simple : le problème de la voiture sur la colline.
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@inproceedings{PUB00024732, author = {Chapel, L. and Deffuant, G.}, title = {Utiliser des machines à vecteurs de support pour approcher les contours d'une fonction valeur dans des problèmes d'atteinte de cible}, title = {Using Support Vector Machines to approach value function contours in case of reaching target problems}, bookTitle = {12ème Journée Scientifique de l'Ecole Doctorale Sciences Pour l'Ingénieur Apprentisage Statistique Apprentissage Symbolique, 04/06/2008-04/06/2008, Clermont Ferrand, FRA}, pages = {10}, url = {http://cemadoc.irstea.fr/cemoa/PUB00024732}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {Nous proposons d'utiliser un algorithme d'apprentissage particulier, les SVMs, pour résoudre des problèmes d'atteinte de cible en temps minimal. La cible correspond à un état souhaité, en sachant que le système se détériore dans une certaine région de l'espace (lorsqu'il transgresse un ensemble de contraintes de viabilité). Le bassin de capture au temps t correspond à l'ensemble des états qui peuvent atteindre la cible en un temps inférieur ou égal à t, sans quitter l'ensemble des contrainte de viabilité. Les frontières d'un bassin de capture au temps t correspondent alors aux contours d'une fonction valeur au temps t. Les bassins de capture peuvent alors être utilisés pour définir une fonction de contrôle qui permet au système d'atteindre la cible en un temps minimal. Nous proposons une nouvelle approche, basée sur les SVMs, qui permet d'approcher les bassins de capture successifs et définissons une procédure de contrôle qui permet de contrôler le système afin qu'il atteigne la cible. Nous illustrons cette méthode sur un exemple simple : le problème de la voiture sur la colline.}, }
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F. Chuffart, T. Faure, N. Dumoulin, R. Reuillon, G. Deffuant
Design and analysis of computer experiments with SimExplorer
ESM'2008 European Simulation and Modelling Conference, 27/10/2008-29/10/2008, Le Havre, FRA (p. 575-577), EUROSIS, 2008
abs web bib

SimExplorer is a framework that includes an API and an IDE dedicated to design and analysis of computer experiments. SimExplorer combines blind computing on demand service access, traceability and reporting features and sensitivity analysis tools. This tutorial provides the concepts and exemplifies a typical use of SimExplorer, performing a global sensitivity analysis of a given individual-based predator prey model.
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@inproceedings{PUB00024933, author = {Chuffart, F. and Faure, T. and Dumoulin, N. and Reuillon, R. and Deffuant, G.}, title = {Design and analysis of computer experiments with SimExplorer}, title = {Conception et analyse de plans d'expériences avec SimExplorer}, bookTitle = {ESM'2008 European Simulation and Modelling Conference, 27/10/2008-29/10/2008, Le Havre, FRA}, publisher = {EUROSIS}, pages = {575-577}, url = {http://cemadoc.irstea.fr/cemoa/PUB00024933}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {SimExplorer is a framework that includes an API and an IDE dedicated to design and analysis of computer experiments. SimExplorer combines blind computing on demand service access, traceability and reporting features and sensitivity analysis tools. This tutorial provides the concepts and exemplifies a typical use of SimExplorer, performing a global sensitivity analysis of a given individual-based predator prey model. }, }
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B. Gandar, G. Deffuant, G. Loosli
Les suites à discrépance faible : un moyen de réduire le nombre de vecteurs supports des SVMs
12ème Journée Scientifique de l'Ecole Doctorale Sciences Pour l'Ingénieur Apprentisage Statistique Apprentissage Symbolique, 04/06/2008-04/06/2008, Clermont Ferrand, FRA (p. 9), 2008
abs web bib

L'apprentissage statistique consiste à déterminer une fonction mathématique à partir d'exemples supposés indépendants et identiquement distribués. Dans le cadre de l'apprentissage actif, nous pouvons choisir ces exemples. Des travaux théoriques dans le cas de la régression, ont prouvé que l'utilisation d'une base d'apprentissage issue de suites à discrépance faible permettait d'améliorer la vitesse de convergence des algorithmes d'apprentissage. Des expériences numériques, réalisées en classification avec des réseaux de neurones, ont montré que l'utilisation de ces suites augmente la qualité d'apprentissage. Ce papier reprend les résultats théoriques connus en régression et explique pourquoi ceux-ci ne se transposent pas en classification. Il présente également des tests numériques sur l'algorithme de classification des SVMs (Support Vector Machine ou Séparateur à Vaste Marge) avec des bases d'apprentissage issues de suites à discrépance faible. Les résultats obtenus ne montrent pas une amélioration de la performance, mais les SVMs obtenus sont plus compacts : ce qui peut engendrer un gain de vitesse de prédiction dans des applications de ces derniers.
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@inproceedings{PUB00024705, author = {Gandar, B. and Deffuant, G. and Loosli, G.}, title = {Les suites à discrépance faible : un moyen de réduire le nombre de vecteurs supports des SVMs}, title = {The low discrepancy sequences: a way of reducing the number of supports vectors of SVMs}, bookTitle = {12ème Journée Scientifique de l'Ecole Doctorale Sciences Pour l'Ingénieur Apprentisage Statistique Apprentissage Symbolique, 04/06/2008-04/06/2008, Clermont Ferrand, FRA}, pages = {9}, url = {http://cemadoc.irstea.fr/cemoa/PUB00024705}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {L'apprentissage statistique consiste à déterminer une fonction mathématique à partir d'exemples supposés indépendants et identiquement distribués. Dans le cadre de l'apprentissage actif, nous pouvons choisir ces exemples. Des travaux théoriques dans le cas de la régression, ont prouvé que l'utilisation d'une base d'apprentissage issue de suites à discrépance faible permettait d'améliorer la vitesse de convergence des algorithmes d'apprentissage. Des expériences numériques, réalisées en classification avec des réseaux de neurones, ont montré que l'utilisation de ces suites augmente la qualité d'apprentissage. Ce papier reprend les résultats théoriques connus en régression et explique pourquoi ceux-ci ne se transposent pas en classification. Il présente également des tests numériques sur l'algorithme de classification des SVMs (Support Vector Machine ou Séparateur à Vaste Marge) avec des bases d'apprentissage issues de suites à discrépance faible. Les résultats obtenus ne montrent pas une amélioration de la performance, mais les SVMs obtenus sont plus compacts : ce qui peut engendrer un gain de vitesse de prédiction dans des applications de ces derniers.}, }
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S. Huet, G. Deffuant
Bounded confidence with rejection: the infinite population limit with perfect uniform initial density
Modèles et Apprentissages en Sciences Humaines et Sociales (MASH), 05/06/2008-06/06/2008, Créteil, FRA (p. 10), 2008
abs web bib

Huet and Deffuant (2007) propose a new opinion dynamics model based on the bounded confidence principles, with a rejection mechanism. The simulations of the agent-based model show that this new model leads generally to fewer clusters than the classical bounded confidence model. We build an aggregated model of this agent-based model (ABM), considering the limit case of an infinite population, in order to better understand the clustering process in the ABM. The dynamics of the aggregated model, starting from a perfectly uniform distribution of opinions, and the dynamics of the ABM are significantly different. However, the aggregated model provides relevant information about how the rejection mechanism and bounding the attitude space influence the clustering process. It firstly outlines that, with a perfectly symmetric density, the clustering process is almost impossible and that the only final stable state is one centred cluster. Secondly we notice that one centred cluster can be lead with the only rejection mechanism or with an unbounded attitude space.
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@inproceedings{PUB00024188, author = {Huet, S. and Deffuant, G.}, title = {Bounded confidence with rejection: the infinite population limit with perfect uniform initial density}, title = {Confiance limitée et rejet: l'effet d'une taille de population infinie pour une densité initiale parfaitement uniforme}, bookTitle = {Modèles et Apprentissages en Sciences Humaines et Sociales (MASH), 05/06/2008-06/06/2008, Créteil, FRA}, pages = {10}, url = {http://cemadoc.irstea.fr/cemoa/PUB00024188}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {Huet and Deffuant (2007) propose a new opinion dynamics model based on the bounded confidence principles, with a rejection mechanism. The simulations of the agent-based model show that this new model leads generally to fewer clusters than the classical bounded confidence model. We build an aggregated model of this agent-based model (ABM), considering the limit case of an infinite population, in order to better understand the clustering process in the ABM. The dynamics of the aggregated model, starting from a perfectly uniform distribution of opinions, and the dynamics of the ABM are significantly different. However, the aggregated model provides relevant information about how the rejection mechanism and bounding the attitude space influence the clustering process. It firstly outlines that, with a perfectly symmetric density, the clustering process is almost impossible and that the only final stable state is one centred cluster. Secondly we notice that one centred cluster can be lead with the only rejection mechanism or with an unbounded attitude space.}, }
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S. Huet, G. Deffuant
Bounded confidence with rejection: clusters or scattered opinions ?
5th Conference of the European Social Simulation Association ESSA 2008, 01/09/2008-05/09/2008, Brescia, ITA / Proceedings of the Fifth Conference of the European Social Simulation Association (ESSA'08) (p. 12), University of Brescia, Brescia, ITA, 2008
abs web bib

Huet and Deffuant (2007) propose a new opinion dynamics model based on the bounded confidence principles, with a rejection mechanism. We study new simulations of the agent-based model for a population of 10000 individuals. We generally observe fewer clusters than the classical bounded confidence model, and below a threshold of the uncertainty, no cluster appear: all opinions remain scattered. We build an aggregated model of this agent-based model (ABM), in the limit case of an infinite population, in order to better understand this dynamical behaviour. When adding a small perturbation in the initial distribution, the aggregated model and ABM yield similar numbers of clusters for the same parameters. Below a critical value of uncertainty, the aggregated model forms no cluster and the distribution remains uniform. The critical value is higher for the aggregated model than for the ABM, indicating a finite size effect that we discuss.
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@inproceedings{PUB00024581, author = {Huet, S. and Deffuant, G.}, title = {Bounded confidence with rejection: clusters or scattered opinions ?}, title = {Confiance bornée avec rejet: organisation en groupe d'opinion ou changement permanent d'opinion}, bookTitle = {5th Conference of the European Social Simulation Association ESSA 2008, 01/09/2008-05/09/2008, Brescia, ITA / Proceedings of the Fifth Conference of the European Social Simulation Association (ESSA'08)}, address = {Brescia, ITA}, publisher = {University of Brescia}, pages = {12}, url = {http://cemadoc.irstea.fr/cemoa/PUB00024581}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {Huet and Deffuant (2007) propose a new opinion dynamics model based on the bounded confidence principles, with a rejection mechanism. We study new simulations of the agent-based model for a population of 10000 individuals. We generally observe fewer clusters than the classical bounded confidence model, and below a threshold of the uncertainty, no cluster appear: all opinions remain scattered. We build an aggregated model of this agent-based model (ABM), in the limit case of an infinite population, in order to better understand this dynamical behaviour. When adding a small perturbation in the initial distribution, the aggregated model and ABM yield similar numbers of clusters for the same parameters. Below a critical value of uncertainty, the aggregated model forms no cluster and the distribution remains uniform. The critical value is higher for the aggregated model than for the ABM, indicating a finite size effect that we discuss.}, }
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I. Alvarez, S. Bernard, G. Deffuant
Keep the decision tree and estimate the class probabilities using its decision boundary
International Joint Conference of Artificial Intelligence, Hyderabad, IND, 7-12 janvier 2007 (p. 6), 2007
abs web bib

This paper proposes a new method to estimate the class membership probability of the cases classified by a Decision Tree. This method provides smooth class probabilities estimate, without any modification of the tree, when the data are numerical. It applies a posteriori and doesn't use additional training cases. It relies on the distance to the decision boundary induced by the decision tree. The distance is computed on the training sample. It is then used as an input for a very simple one dimension kernel-based density estimator, which provides an estimate of the class membership probability. This geometric method gives good results even with pruned trees, so the intelligibility of the tree is fully preserved. / Cet article propose une nouvelle méthode pour estimer les probabilités d'appartenance aux classes des cas classés par un arbre de décision. Cette méthode produit des estimateurs de probabilités qui varient avec les exemples, et sans modification de l'arbre, dès lors que les données sont numériques. La méthode s'applique a posteriori et ne requiert pas d'exemples d'apprentissage supplémentaires. Elle repose sur la frontière de décision induite par l'arbre de décision. Cette distance est calculée sur la base d'apprentissage. Elle est ensuite fournie à un estimateur de densité à noyau qui calcule la probabilité d'appartenance à chaque classe. Cette méthode géométrique donne de bons résultats même après élagage, l'intelligibilité des arbres est donc complètement préservée.
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@inproceedings{PUB00020610, author = {Alvarez, I. and Bernard, S. and Deffuant, G.}, title = {Keep the decision tree and estimate the class probabilities using its decision boundary}, title = {Garder l'arbre de décision et estimer la probabilité d'appartenance aux classes en utilisant sa frontière de décision}, bookTitle = {International Joint Conference of Artificial Intelligence, Hyderabad, IND, 7-12 janvier 2007}, pages = {6}, url = {http://www.ijcai07.org}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00020610}, year = {2007}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {This paper proposes a new method to estimate the class membership probability of the cases classified by a Decision Tree. This method provides smooth class probabilities estimate, without any modification of the tree, when the data are numerical. It applies a posteriori and doesn't use additional training cases. It relies on the distance to the decision boundary induced by the decision tree. The distance is computed on the training sample. It is then used as an input for a very simple one dimension kernel-based density estimator, which provides an estimate of the class membership probability. This geometric method gives good results even with pruned trees, so the intelligibility of the tree is fully preserved. / Cet article propose une nouvelle méthode pour estimer les probabilités d'appartenance aux classes des cas classés par un arbre de décision. Cette méthode produit des estimateurs de probabilités qui varient avec les exemples, et sans modification de l'arbre, dès lors que les données sont numériques. La méthode s'applique a posteriori et ne requiert pas d'exemples d'apprentissage supplémentaires. Elle repose sur la frontière de décision induite par l'arbre de décision. Cette distance est calculée sur la base d'apprentissage. Elle est ensuite fournie à un estimateur de densité à noyau qui calcule la probabilité d'appartenance à chaque classe. Cette méthode géométrique donne de bons résultats même après élagage, l'intelligibilité des arbres est donc complètement préservée.}, }
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L. Chapel, G. Deffuant
SVM viability controller active learning: application to bike Control
IEEE International Symposium on Approximate Dynamic Programming and Reinforcement Learning (ADPRL'07), Hawaï, USA, 1-4 april 2007 (p. 8), 2007
abs web bib

It was shown recently that SVMs are particularly adequate to define action policies to keep a dynamical system inside a given constraint set (in the framework of viability theory). However, the training set of the SVMs face the dimensionality curse, because it is based on a regular grid of the state space. In this paper, we propose an active learning approach, aiming at decreasing dramatically the training set size, keeping it as close as possible to the final number of support vectors. We use a virtual multi-resolution grid, and some particularities of the problem, to choose very efficient examples to add to the training set. To illustrate the performances of the algorithm, we solve a six-dimensional problem, controlling a bike on a track, problem usually solved using reinforcement learning techniques.
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@inproceedings{PUB00022177, author = {Chapel, L. and Deffuant, G.}, title = {SVM viability controller active learning: application to bike Control}, title = {Apprentissage actif de noyau de viabilité avec des SVMs : application au contrôle d'un vélo}, bookTitle = {IEEE International Symposium on Approximate Dynamic Programming and Reinforcement Learning (ADPRL'07), Hawaï, USA, 1-4 april 2007}, pages = {8}, url = {http://cemadoc.irstea.fr/cemoa/PUB00022177}, year = {2007}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {It was shown recently that SVMs are particularly adequate to define action policies to keep a dynamical system inside a given constraint set (in the framework of viability theory). However, the training set of the SVMs face the dimensionality curse, because it is based on a regular grid of the state space. In this paper, we propose an active learning approach, aiming at decreasing dramatically the training set size, keeping it as close as possible to the final number of support vectors. We use a virtual multi-resolution grid, and some particularities of the problem, to choose very efficient examples to add to the training set. To illustrate the performances of the algorithm, we solve a six-dimensional problem, controlling a bike on a track, problem usually solved using reinforcement learning techniques.}, }
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L. Chapel, S. Martin, G. Deffuant
Lake eutrophication: using resilience evaluation to compute sustainable policies
10th International conference on environmental science and technology - CEST 2007, Kos island, GRC, 5-7 September 2007 (p. 8), 2007
abs web bib

We consider a sustainable management issue: How to maintain a lake in an oligotrophic state (with low input nutrients, clear water and high economic value), notwithstanding the economic interest of farmers which requires to use input nutrients? We adopt Martin [1]'s framework, in which this problem is related to a particular definition of resilience. In a widely accepted definition, resilience is the capacity of a system to maintain some of its properties in spite of disturbance. Martin [1] proposed a precise mathematical interpretation of this concept, based on viability theory, together with methods to compute resilience values and restoration action policies. Resilience values are computed as the inverse of the cost for restoring a given interesting property, lost after a disturbance. This framework is very general, and is in principle of high interest for policy support. However, its current practical implementation is limited to problems in low dimensional space and the uncertainties on the parameters of the model are not taken into account. In this paper, we propose a new algorithm in order to deal with problems in higher dimensional space. It uses a classification method, Support Vector Machines, which is very efficient to deal with problems in high dimensional spaces. In addition, it defines more or less cautious action policies, in order to restore the viability of a system [6]. Starting from this new development, we propose an algorithm that integrates the specificities for computing resilience values, and restoration action policies. We apply this new approach to compute resilience values based on a model of lake eutrophication, including three parameters: the amount of phosphorus in the water, the annual phosphorus input from human activities and the amount of phosphorus in the sediments. We also include uncertainties on some parameters of the dynamical model. The results associated with each state of the system are, in one hand, the cost for restoring the property of interest and, on the other hand, the resilience in relation to potential exogenous disturbances. Comparing the results obtained in this paper with those in the literature, this work highlights the state areas where it is crucial to take into account the slow dynamics of the model (i.e. the amount of phosphorus in the sediments). It also emphasizes that the results are sensitive to the uncertainties on the parameters, precisely the parameters that were neglected when using the classical viability algorithm. To conclude, the combination of the definition of resilience proposed by [1] and the new algorithm of viability introduced in this paper offers an interesting approach to sustainable development, enabling to compute resilience values and restoration action policies on more realistic models than previously.
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@inproceedings{PUB00022178, author = {Chapel, L. and Martin, S. and Deffuant, G.}, title = {Lake eutrophication: using resilience evaluation to compute sustainable policies}, title = {Eutrophisation des lacs : évaluer la résilience pour calculer des politiques durables}, bookTitle = {10th International conference on environmental science and technology - CEST 2007, Kos island, GRC, 5-7 September 2007}, pages = {8}, url = {http://cemadoc.irstea.fr/cemoa/PUB00022178}, year = {2007}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {We consider a sustainable management issue: How to maintain a lake in an oligotrophic state (with low input nutrients, clear water and high economic value), notwithstanding the economic interest of farmers which requires to use input nutrients? We adopt Martin [1]'s framework, in which this problem is related to a particular definition of resilience. In a widely accepted definition, resilience is the capacity of a system to maintain some of its properties in spite of disturbance. Martin [1] proposed a precise mathematical interpretation of this concept, based on viability theory, together with methods to compute resilience values and restoration action policies. Resilience values are computed as the inverse of the cost for restoring a given interesting property, lost after a disturbance. This framework is very general, and is in principle of high interest for policy support. However, its current practical implementation is limited to problems in low dimensional space and the uncertainties on the parameters of the model are not taken into account. In this paper, we propose a new algorithm in order to deal with problems in higher dimensional space. It uses a classification method, Support Vector Machines, which is very efficient to deal with problems in high dimensional spaces. In addition, it defines more or less cautious action policies, in order to restore the viability of a system [6]. Starting from this new development, we propose an algorithm that integrates the specificities for computing resilience values, and restoration action policies. We apply this new approach to compute resilience values based on a model of lake eutrophication, including three parameters: the amount of phosphorus in the water, the annual phosphorus input from human activities and the amount of phosphorus in the sediments. We also include uncertainties on some parameters of the dynamical model. The results associated with each state of the system are, in one hand, the cost for restoring the property of interest and, on the other hand, the resilience in relation to potential exogenous disturbances. Comparing the results obtained in this paper with those in the literature, this work highlights the state areas where it is crucial to take into account the slow dynamics of the model (i.e. the amount of phosphorus in the sediments). It also emphasizes that the results are sensitive to the uncertainties on the parameters, precisely the parameters that were neglected when using the classical viability algorithm. To conclude, the combination of the definition of resilience proposed by [1] and the new algorithm of viability introduced in this paper offers an interesting approach to sustainable development, enabling to compute resilience values and restoration action policies on more realistic models than previously. }, }
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S. Huet, G. Deffuant
Sensitivity of primacy effect to interactions
EuroCogSci07, Delphes, GRC, 23-27 mai 2007 / Proceedings of EuroCogSci07/Stella Vosniadou, Daniel Kayser, Athanassios Protopapas (p. 830-835), Hellenic Cognitive Science Society, 2007
abs web bib

We propose an individual based model of attitude dynamics which, in some conditions, reproduces primacy effect behaviours. The primacy effect takes place when the attitude of an individual depends on the reception order of features describing an object. Typically, when receiving a strong negative feature first, the individual keeps a negative attitude whatever the number of moderate positive features it receives afterwards. We consider a population of individuals which receive the features from a media, and communicate with each other: in some cases, interactions increase the number of individuals exhibiting a primacy effect, in other cases they decrease this number. We study the sensitivity of this phenomenon to the interaction structure and to the part of the population with an initial negative attitude.
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@inproceedings{PUB00021807, author = {Huet, S. and Deffuant, G.}, title = {Sensitivity of primacy effect to interactions}, title = {Impact de l'interaction sur l'effet de primauté}, bookTitle = {EuroCogSci07, Delphes, GRC, 23-27 mai 2007 / Proceedings of EuroCogSci07/Stella Vosniadou, Daniel Kayser, Athanassios Protopapas}, address = {Hellenic Cognitive Science Society}, pages = {830-835}, url = {http://cemadoc.irstea.fr/cemoa/PUB00021807}, year = {2007}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {We propose an individual based model of attitude dynamics which, in some conditions, reproduces primacy effect behaviours. The primacy effect takes place when the attitude of an individual depends on the reception order of features describing an object. Typically, when receiving a strong negative feature first, the individual keeps a negative attitude whatever the number of moderate positive features it receives afterwards. We consider a population of individuals which receive the features from a media, and communicate with each other: in some cases, interactions increase the number of individuals exhibiting a primacy effect, in other cases they decrease this number. We study the sensitivity of this phenomenon to the interaction structure and to the part of the population with an initial negative attitude.}, }
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S. Huet, G. Deffuant
When do interactions increase or decrease primacy effect?
M2M 2007, Third International Model-to-Model Workshop, Marseille, France, 15-16 mars 2007 (p. 102-120), 2007
abs web bib

We propose an individual based model of attitude dynamics which, in some conditions, reproduces primacy effect behaviours. The primacy effect takes place when the attitude of an individual depends on the reception order of features describing an object. Typically, when receiving a strong negative feature first, the individual keeps a negative attitude whatever the number of moderate positive features it receives afterwards. We consider a population of individuals which receive the features from a media, and communicate with each other: in some cases, interactions increase the number of individuals exhibiting a primacy effect, in other cases they decrease this number. To better understand this phenomenon, we developed aggregated models of the individual based model with interaction.
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@inproceedings{PUB00022656, author = {Huet, S. and Deffuant, G.}, title = {When do interactions increase or decrease primacy effect?}, title = {Quand l'interaction faire croître ou décroître l'effet de primauté}, bookTitle = {M2M 2007, Third International Model-to-Model Workshop, Marseille, France, 15-16 mars 2007}, pages = {102-120}, url = {http://cemadoc.irstea.fr/cemoa/PUB00022656}, year = {2007}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {We propose an individual based model of attitude dynamics which, in some conditions, reproduces primacy effect behaviours. The primacy effect takes place when the attitude of an individual depends on the reception order of features describing an object. Typically, when receiving a strong negative feature first, the individual keeps a negative attitude whatever the number of moderate positive features it receives afterwards. We consider a population of individuals which receive the features from a media, and communicate with each other: in some cases, interactions increase the number of individuals exhibiting a primacy effect, in other cases they decrease this number. To better understand this phenomenon, we developed aggregated models of the individual based model with interaction.}, }
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S. Huet, G. Deffuant, W. Jager
Des dynamiques de différenciation individuelle peuvent accroître le conformisme global
ARCo'07, Cognition - Complexité - Collectif, Nancy - Loria, 28-30 novembre 2007 (p. 89-102), Acta-Cognitica, Nancy - Loria, 2007
abs web bib

Dans le modèle de dynamiques d'attitudes (ou opinions) à "confiance limitée" (CL), deux individus se rapprochent lors d'une rencontre si leur différence est inférieure à un seuil. Nous considérons des individus avec deux attitudes, et nous ajoutons au modèle CL un mécanisme de rejet. Si deux individus sont très éloignés sur la première attitude et très proches sur la seconde, alors ils résolvent la contradiction en s'éloignant l'un de l'autre sur la seconde attitude. En considérant une population d'individus initialement aléatoirement distribués, le modèle exhibe des attracteurs composés de groupes métastables dans l'espace 2D, qui se maintiennent dans une compétition entre attraction et rejet. L'analyse du modèle et les simulations montrent que le nombre final de groupes croît linéairement avec l'inverse de l'incertitude des individus, alors qu'il croît quadratiquement dans le modèle CL en 2D.
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@inproceedings{PUB00022902, author = {Huet, S. and Deffuant, G. and Jager, W.}, title = {Des dynamiques de différenciation individuelle peuvent accroître le conformisme global}, title = {Individual differentiation dynamic can increase the global conformism}, bookTitle = {ARCo'07, Cognition - Complexité - Collectif, Nancy - Loria, 28-30 novembre 2007}, address = {Nancy - Loria}, publisher = {Acta-Cognitica}, pages = {89-102}, url = {http://cemadoc.irstea.fr/cemoa/PUB00022902}, year = {2007}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; FACULTY OF ECONOMICS UNIVERSITY OF GRONINGEN NLD}, abstract = {Dans le modèle de dynamiques d'attitudes (ou opinions) à "confiance limitée" (CL), deux individus se rapprochent lors d'une rencontre si leur différence est inférieure à un seuil. Nous considérons des individus avec deux attitudes, et nous ajoutons au modèle CL un mécanisme de rejet. Si deux individus sont très éloignés sur la première attitude et très proches sur la seconde, alors ils résolvent la contradiction en s'éloignant l'un de l'autre sur la seconde attitude. En considérant une population d'individus initialement aléatoirement distribués, le modèle exhibe des attracteurs composés de groupes métastables dans l'espace 2D, qui se maintiennent dans une compétition entre attraction et rejet. L'analyse du modèle et les simulations montrent que le nombre final de groupes croît linéairement avec l'inverse de l'incertitude des individus, alors qu'il croît quadratiquement dans le modèle CL en 2D.}, }
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S. Huet, G. Deffuant, W. Jager
Rejection mechanism in 2D bounded confidence provides more conformity
ECCS'07, European Conference on Complex Systems, Dresden, Allemagne (DEU) 1-6 october 2007 (p. 16), 2007
abs web bib

This paper explores the dynamics of attitude change on 2 dimensions (2D) as a result of social interaction. We add a rejection mechanism into a 2D bounded confidence (BC) model. The principle is that one shifts away from a close attitude of one's interlocutor, when there is a strong disagreement on the other attitude. The model shows metastable clusters, which maintain themselves through opposite influences of competitor clusters. Our analysis and first experiments support the hypothesis that the number of clusters grows linearly with the inverse of the uncertainty, whereas this growth is quadratic in the BC model.
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@inproceedings{PUB00022655, author = {Huet, S. and Deffuant, G. and Jager, W.}, title = {Rejection mechanism in 2D bounded confidence provides more conformity}, title = {Un mécanisme de rejet au sein d'un modèle de confiance limitée deux dimensions engendre davantage de conformisme}, bookTitle = {ECCS'07, European Conference on Complex Systems, Dresden, Allemagne (DEU) 1-6 october 2007}, pages = {16}, url = {http://cemadoc.irstea.fr/cemoa/PUB00022655}, year = {2007}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; FACULTY OF ECONOMICS UNIVERSITY OF GRONINGEN PAYS- BAS NLD}, abstract = {This paper explores the dynamics of attitude change on 2 dimensions (2D) as a result of social interaction. We add a rejection mechanism into a 2D bounded confidence (BC) model. The principle is that one shifts away from a close attitude of one's interlocutor, when there is a strong disagreement on the other attitude. The model shows metastable clusters, which maintain themselves through opposite influences of competitor clusters. Our analysis and first experiments support the hypothesis that the number of clusters grows linearly with the inverse of the uncertainty, whereas this growth is quadratic in the BC model.}, }
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L. Chapel, G. Deffuant
SVM viability controller active learning
Kernel machines and Reinforcement Learning Workshop - International Conference on Machine Learning 2006. Pittsburgh, USA, 25-29 June 2006 (p. 7), 2006
abs web bib

We use support vector machines (SVMs) to compute the actions which maintain a dynamical system within a defined subset of its state space. The principles of our method are inspired by the viability theory. We use SVMs to approximate the viability kernel which is the set of states from which it is possible to maintain the system. The actions to perform on the system can then be easily computed from the SVM, whatever the starting point. The major limitation of the approach is the exponentially growing number of training examples when the dimension of the state space increases. We use active learning to limit this number.
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@inproceedings{PUB00020449, author = {Chapel, L. and Deffuant, G.}, title = {SVM viability controller active learning}, title = {Apprentissage actif par contrôleur de viabilité par Support vector machines}, bookTitle = {Kernel machines and Reinforcement Learning Workshop - International Conference on Machine Learning 2006. Pittsburgh, USA, 25-29 June 2006}, pages = {7}, url = {http://www.grappa.univ-lille3.fr/~ppreux/krl/krl.html}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00020449}, year = {2006}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {We use support vector machines (SVMs) to compute the actions which maintain a dynamical system within a defined subset of its state space. The principles of our method are inspired by the viability theory. We use SVMs to approximate the viability kernel which is the set of states from which it is possible to maintain the system. The actions to perform on the system can then be easily computed from the SVM, whatever the starting point. The major limitation of the approach is the exponentially growing number of training examples when the dimension of the state space increases. We use active learning to limit this number.}, }
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G. Deffuant, S. Huet
Propagation effects of filtering incongruent information
Agent Based Model of Consumer Behaviour Workshop, Janvier 2006, Guilford, GBR (p. 8), 2006
abs web bib

We propose a simple individual-based model of information filtering and study some of its implications on the attitude about an object. The model assumes that a filter selects only important features, with a higher threshold of importance when the attitude about the feature is incongruent with the global attitude about the object. Moreover, we suppose that individuals transmit only features which are congruent with their global attitude. We consider two variants of this model. For both of them, different orders of feature reception can lead to different attitudes. For instance, an individual with a positive attitude about the object, can finally become negative, even though the object is globally neutral (the sum of the feature attitudes is 0). The interactions among individuals can significantly increase the probability of such non-rational attitudes.
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@inproceedings{PUB00020382, author = {Deffuant, G. and Huet, S.}, title = {Propagation effects of filtering incongruent information}, title = {Effet sur la diffusion du filtrage des informations incongruentes}, bookTitle = {Agent Based Model of Consumer Behaviour Workshop, Janvier 2006, Guilford, GBR}, pages = {8}, url = {http://cemadoc.irstea.fr/cemoa/PUB00020382}, year = {2006}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {We propose a simple individual-based model of information filtering and study some of its implications on the attitude about an object. The model assumes that a filter selects only important features, with a higher threshold of importance when the attitude about the feature is incongruent with the global attitude about the object. Moreover, we suppose that individuals transmit only features which are congruent with their global attitude. We consider two variants of this model. For both of them, different orders of feature reception can lead to different attitudes. For instance, an individual with a positive attitude about the object, can finally become negative, even though the object is globally neutral (the sum of the feature attitudes is 0). The interactions among individuals can significantly increase the probability of such non-rational attitudes.}, }
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G. Deffuant, S. Huet
Collective reinforcement of first impression Bias
WCSS'06 The First World Congress on Social Simulation, Kyoto (Japon) 21-25 aout 2006 (p. 8), 2006
abs web bib

We propose a simple model of attitude dynamics in which an agent tends to ignore the features which contradict its views. For instance, having received a first very negative feature, the agent may stop to consider any moderately positive feature. We call this phenomenon first impression bias (FIB). We consider a population of agents which are all in contact with a media, communicating randomly chosen features of an object. In some cases, we observe on simulations that FIB is significantly more frequent when the agents interact with each other than when they are only in contact with the media. We design an analytical aggregated model of the global agent-based model behaviour which helps to explain the higher number of FIB due to the interactions.
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@inproceedings{PUB00020378, author = {Deffuant, G. and Huet, S.}, title = {Collective reinforcement of first impression Bias}, title = {Renforcement collectif du bias de première impression}, bookTitle = {WCSS'06 The First World Congress on Social Simulation, Kyoto (Japon) 21-25 aout 2006}, pages = {8}, url = {http://cemadoc.irstea.fr/cemoa/PUB00020378}, year = {2006}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {We propose a simple model of attitude dynamics in which an agent tends to ignore the features which contradict its views. For instance, having received a first very negative feature, the agent may stop to consider any moderately positive feature. We call this phenomenon first impression bias (FIB). We consider a population of agents which are all in contact with a media, communicating randomly chosen features of an object. In some cases, we observe on simulations that FIB is significantly more frequent when the agents interact with each other than when they are only in contact with the media. We design an analytical aggregated model of the global agent-based model behaviour which helps to explain the higher number of FIB due to the interactions.}, }
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S. Huet, G. Deffuant
Effets d'un filtre cognitif sur la diffusion d'information
MOSIM'06, 6ème Conférence Francophone de Modélisation, Simulation, Rabat, MAR, 3 au 5 avril 2006 (p. 10), 2006
abs web bib

Les recherches sur la diffusion de l'information montrent que les individus ne la retiennent et ne la propagent pas nécessairement. Nous proposons un modèle simple de ce phénomène. Les individus s'échangent des informations relatives à un objet décrit par des facettes dont l'utilité est positive ou négative. La possession d'une information correspond au fait de disposer de l'utilité d'une facette. Les individus disposent par ailleurs d'une opinion globale a priori sur l'objet. Lors des discussions, les facettes dont l'utilité en valeur absolue est inférieure à un seuil d'intérêt sont ignorées et ne sont pas reçues. Ce seuil est plus élevé lorsque l'utilité et l'opinion globale sont de signes contraires. En outre, un individu ne parle pas des facettes qu'il possède lorsque leur utilité est de signe contraire à son opinion globale. L'étude du modèle à convergence, lorsque tous échangent avec tous, permet le recensement des états finaux et souligne l'importance des caractéristiques des premiers individus qui reçoivent l'information. Nous étudions le modèle pour une population dont les individus échangent avec un nombre constant et faible de voisins, dans le cas «une seule information, de même utilité pour tous, un seul individu source initial » grâce à un calcul approché de la distribution de probabilités du nombre final d'individus possédant l'information. Le nombre de voisins modifie cette distribution car il limite la rencontre entre des individus à même de diffuser l'information
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@inproceedings{PUB00019444, author = {Huet, S. and Deffuant, G.}, title = {Effets d'un filtre cognitif sur la diffusion d'information}, title = {Cognitive filter effects on the information diffusion process}, bookTitle = {MOSIM'06, 6ème Conférence Francophone de Modélisation, Simulation, Rabat, MAR, 3 au 5 avril 2006}, pages = {10}, url = {http://cemadoc.irstea.fr/cemoa/PUB00019444}, year = {2006}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {Les recherches sur la diffusion de l'information montrent que les individus ne la retiennent et ne la propagent pas nécessairement. Nous proposons un modèle simple de ce phénomène. Les individus s'échangent des informations relatives à un objet décrit par des facettes dont l'utilité est positive ou négative. La possession d'une information correspond au fait de disposer de l'utilité d'une facette. Les individus disposent par ailleurs d'une opinion globale a priori sur l'objet. Lors des discussions, les facettes dont l'utilité en valeur absolue est inférieure à un seuil d'intérêt sont ignorées et ne sont pas reçues. Ce seuil est plus élevé lorsque l'utilité et l'opinion globale sont de signes contraires. En outre, un individu ne parle pas des facettes qu'il possède lorsque leur utilité est de signe contraire à son opinion globale. L'étude du modèle à convergence, lorsque tous échangent avec tous, permet le recensement des états finaux et souligne l'importance des caractéristiques des premiers individus qui reçoivent l'information. Nous étudions le modèle pour une population dont les individus échangent avec un nombre constant et faible de voisins, dans le cas «une seule information, de même utilité pour tous, un seul individu source initial » grâce à un calcul approché de la distribution de probabilités du nombre final d'individus possédant l'information. Le nombre de voisins modifie cette distribution car il limite la rencontre entre des individus à même de diffuser l'information}, }
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L. Chapel, G. Deffuant, S. Martin, C. Mullon
Defining yield policies in a viability theory approach
5th European conference on ecological modeling, Pushchino, RUSSIE, 19-23 septembre 2005 (p. 3), 2005
abs web bib

Within the Southern Benguela ecosystem, five different groups (detritus, phytoplankton, zooplankton, pelagic fish and demersal fish) were considered by (Mullon et al., 2004) in a dynamical model of biomass evolution. They studied this model in a viability perspective, trying to assess, for a given constant yield, whether each species biomass remains inside a given interval, taking into account the uncertainty on the interaction coefficients. Instead of studying the healthy states of this marine ecosystem with a constant yield, we focus here on the yield policies which keep the system viable. Using the mathematical concept of viability kernel (Aubin, 1991), we examine how yield management might guarantee viable fisheries. Numerical simulations are provided to illustrate the main findings.
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@inproceedings{PUB00018512, author = {Chapel, L. and Deffuant, G. and Martin, S. and Mullon, C.}, title = {Defining yield policies in a viability theory approach}, title = {Définir des politiques de pêches en utilisant la théorie de la viabilité}, bookTitle = {5th European conference on ecological modeling, Pushchino, RUSSIE, 19-23 septembre 2005}, pages = {3}, url = {http://cemadoc.irstea.fr/cemoa/PUB00018512}, year = {2005}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; IRD GEODES}, abstract = {Within the Southern Benguela ecosystem, five different groups (detritus, phytoplankton, zooplankton, pelagic fish and demersal fish) were considered by (Mullon et al., 2004) in a dynamical model of biomass evolution. They studied this model in a viability perspective, trying to assess, for a given constant yield, whether each species biomass remains inside a given interval, taking into account the uncertainty on the interaction coefficients. Instead of studying the healthy states of this marine ecosystem with a constant yield, we focus here on the yield policies which keep the system viable. Using the mathematical concept of viability kernel (Aubin, 1991), we examine how yield management might guarantee viable fisheries. Numerical simulations are provided to illustrate the main findings.}, }
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G. Deffuant, W. Jager, S. Moss
Dialogues concerning a (possibly) new science
Conference of the European Social Simulation Association, ESSA, Koblenz-Landau University September 59, 2005 (p. 9), 2005
abs web bib

The three characters, Dreamer, Experimentalist and Realistic, meet in an ideal place of Toscana. They come from different places of the old, decadent and altogether fundamentally renewing Europe of the early 21st century. They were invited in this place to discuss matters of high importance: Do agent based computer simulations offer a venue for a new social science? On what basis such a new science would stand? What role would play experimental approaches developed in social psychology? How to use case studies from the real world? Is there a need to develop a specific methodology of simulation?
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@inproceedings{PUB00018535, author = {Deffuant, G. and Jager, W. and Moss, S.}, title = {Dialogues concerning a (possibly) new science}, title = {Dialogues à propos d'une (éventuelle) nouvelle science}, bookTitle = {Conference of the European Social Simulation Association, ESSA, Koblenz-Landau University September 59, 2005}, pages = {9}, url = {http://cemadoc.irstea.fr/cemoa/PUB00018535}, year = {2005}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; UNIVERSITY OF GRONINGEN NLD ; UNIVERSITY OF MANCHESTER GBR}, abstract = {The three characters, Dreamer, Experimentalist and Realistic, meet in an ideal place of Toscana. They come from different places of the old, decadent and altogether fundamentally renewing Europe of the early 21st century. They were invited in this place to discuss matters of high importance: Do agent based computer simulations offer a venue for a new social science? On what basis such a new science would stand? What role would play experimental approaches developed in social psychology? How to use case studies from the real world? Is there a need to develop a specific methodology of simulation? }, }
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G. Deffuant, S. Martin, L. Chapel
Utiliser des « support vector machines » pour apprendre un noyau de viabilité
MajecSTIC 2005 : Manifestation des Jeunes Chercheurs francophones dans les domaines des STIC, Rennes, 16-18 novembre (p. 195-202), 2005
abs web bib

Nous proposons d'utiliser un algorithme d'apprentissage particulier, les SVMs, pour résoudre des problèmes de viabilité. Différentes procédures ont déjà été proposées pour approcher un noyau de viabilité mais leur application reste difficile car le résultat est alors un ensemble de points, sans définition explicite. La méthode proposée permet de donner une bonne approximation du noyau de viabilité, alors défini par une expression analytique, ce qui permet d'utiliser une méthode d'optimisation pour trouver le meilleur contrôle à chaque pas. Cette propriété permet également de considérer l'optimisation sur plusieurs pas, ce qui donne une meilleure approximation du noyau. Des premières expériences montrent que l'algorithme approche le noyau de viabilité avec une bonne précision, dans des espaces de dimension 2 à 6.
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@inproceedings{PUB00018517, author = {Deffuant, G. and Martin, S. and Chapel, L.}, title = {Utiliser des « support vector machines » pour apprendre un noyau de viabilité}, title = {Using « support vector machines » to approximate viability kernel}, bookTitle = {MajecSTIC 2005 : Manifestation des Jeunes Chercheurs francophones dans les domaines des STIC, Rennes, 16-18 novembre}, pages = {195-202}, url = {http://cemadoc.irstea.fr/cemoa/PUB00018517}, year = {2005}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {Nous proposons d'utiliser un algorithme d'apprentissage particulier, les SVMs, pour résoudre des problèmes de viabilité. Différentes procédures ont déjà été proposées pour approcher un noyau de viabilité mais leur application reste difficile car le résultat est alors un ensemble de points, sans définition explicite. La méthode proposée permet de donner une bonne approximation du noyau de viabilité, alors défini par une expression analytique, ce qui permet d'utiliser une méthode d'optimisation pour trouver le meilleur contrôle à chaque pas. Cette propriété permet également de considérer l'optimisation sur plusieurs pas, ce qui donne une meilleure approximation du noyau. Des premières expériences montrent que l'algorithme approche le noyau de viabilité avec une bonne précision, dans des espaces de dimension 2 à 6. }, }
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S. Huet, M. Edwards, G. Deffuant
Taking into account the variations of social network in the mean-field approximation of the threshold behaviour diffusion model
ESSA Conference Model to Model workshop, Valladolid, ESP, 16-19 septembre 2004 (p. 15), 2004
abs web bib

We compare the individual-based "threshold model" of innovation diffusion in the version which has been studied by Young, with an aggregate model we derived from it. The classical threshold model supposes that an individual adopts a behaviour according to a trade-off between a social pressure and a personal interest. Our study considers only the case where all have the same threshold. We present an aggregated model, which takes into account variations of the neighbourhood sizes, whereas previous work assumed this size fixed. The comparison between the aggregated models (the first one assuming a neighbourhood size and the second one, a variable one) points out an improvement of the approximation in most of the value of parameter space. Remaining differences between both models give us some clues about the specific ability of individual-based model to maintain a minority behaviour which becomes a majority by an addition of stochastic effects. / Nous comparons un modèle individu-centré de diffusion de l`innovation (modèle à seuil) proposé par Young à ses approximations agrégées. Le classique modèle à seuil suppose qu`un individu adopte un comportement en fonction des valeurs relatives de la pression sociale qu`il subit et de son intérêt personnel pour ce comportement. Notre étude considère uniquement le cas où tous les individus ont même seuil. Nous présentons un modèle agrégé qui prend en compte la variation de la taille du voisinage d`un individu à l`autre alors que les précédents travaux supposait ce voisinage de taille constante pour tous les individus. La comparaison entre les modèles agrégés (un à voisinage de taille fixe, l`autre à voisinage de taille variable) montre une amélioration de l`approximation pour la plupart des valeurs de l`espace des paramètres. Les différences restantes entre les deux types de modèles nous fournissent quelques indicateurs sur les spécificités du modèle individu-centré, et notamment sur sa capacité à maintenir au sein de la population un comportement minoritaire qui peut, du fait de la stochasticité du modèle, devenir le comportement de la majorité.
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@inproceedings{PUB00016301, author = {Huet, S. and Edwards, M. and Deffuant, G.}, title = {Taking into account the variations of social network in the mean-field approximation of the threshold behaviour diffusion model}, title = {Prise en compte du caractère aléatoire du réseau social dans une approximation par champ moyen d`un modèle à seuil de diffusion d`un comportement}, bookTitle = {ESSA Conference Model to Model workshop, Valladolid, ESP, 16-19 septembre 2004}, pages = {15}, url = {http://cemadoc.irstea.fr/cemoa/PUB00016301}, year = {2004}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {We compare the individual-based "threshold model" of innovation diffusion in the version which has been studied by Young, with an aggregate model we derived from it. The classical threshold model supposes that an individual adopts a behaviour according to a trade-off between a social pressure and a personal interest. Our study considers only the case where all have the same threshold. We present an aggregated model, which takes into account variations of the neighbourhood sizes, whereas previous work assumed this size fixed. The comparison between the aggregated models (the first one assuming a neighbourhood size and the second one, a variable one) points out an improvement of the approximation in most of the value of parameter space. Remaining differences between both models give us some clues about the specific ability of individual-based model to maintain a minority behaviour which becomes a majority by an addition of stochastic effects. / Nous comparons un modèle individu-centré de diffusion de l`innovation (modèle à seuil) proposé par Young à ses approximations agrégées. Le classique modèle à seuil suppose qu`un individu adopte un comportement en fonction des valeurs relatives de la pression sociale qu`il subit et de son intérêt personnel pour ce comportement. Notre étude considère uniquement le cas où tous les individus ont même seuil. Nous présentons un modèle agrégé qui prend en compte la variation de la taille du voisinage d`un individu à l`autre alors que les précédents travaux supposait ce voisinage de taille constante pour tous les individus. La comparaison entre les modèles agrégés (un à voisinage de taille fixe, l`autre à voisinage de taille variable) montre une amélioration de l`approximation pour la plupart des valeurs de l`espace des paramètres. Les différences restantes entre les deux types de modèles nous fournissent quelques indicateurs sur les spécificités du modèle individu-centré, et notamment sur sa capacité à maintenir au sein de la population un comportement minoritaire qui peut, du fait de la stochasticité du modèle, devenir le comportement de la majorité.}, }
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S. Huet, M. Edwards, G. Deffuant
Taking into account the variations of social network in the mean-field approximation of the threshold behaviour diffusion model
ESSA Conference, Model to Model workshop, Valladolid, ESP, 16-19/09/2004 (p. 15), 2004
abs web bib

We compare the individual-based "threshold model" of innovation diffusion in the version which has been studied by Young, with an aggregate model we derived from it. The classical threshold model supposes that an individual adopts a behaviour according to a trade-off between a social pressure and a personal interest. Our study considers only the case where all have the same threshold. We present an aggregated model, which takes into account variations of the neighbourhood sizes, whereas previous work assumed this size fixed. The comparison between the aggregated models (the first one assuming a neighbourhood size and the second one, a variable one) points out an improvement of the approximation in most of the value of parameter space. Remaining differences between both models give us some clues about the specific ability of individual-based model to maintain a minority behaviour which becomes a majority by an addition of stochastic effects. / Nous comparons un modèle individu-centré de diffusion de l`innovation (modèle à seuil) proposé par Young à ses approximations agrégées. Le classique modèle à seuil suppose qu`un individu adopte un comportement en fonction des valeurs relatives de la pression sociale qu`il subit et de son intérêt personnel pour ce comportement. Notre étude considère uniquement le cas où tous les individus ont même seuil. Nous présentons un modèle agrégé qui prend en compte la variation de la taille du voisinage d`un individu à l`autre alors que les précédents travaux supposait ce voisinage de taille constante pour tous les individus. La comparaison entre les modèles agrégés (un à voisinage de taille fixe, l`autre à voisinage de taille variable) montre une amélioration de l`approximation pour la plupart des valeurs de l`espace des paramètres. Les différences restantes entre les deux types de modèles nous fournissent quelques indicateurs sur les spécificités du modèle individu-centré, et notamment sur sa capacité à maintenir au sein de la population un comportement minoritaire qui peut, du fait de la stochasticité du modèle, devenir le comportement de la majorité.
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@inproceedings{PUB00017647, author = {Huet, S. and Edwards, M. and Deffuant, G.}, title = {Taking into account the variations of social network in the mean-field approximation of the threshold behaviour diffusion model}, title = {Prise en compte du caractère aléatoire du réseau social dans une approximation par champs moyen d`un modèle à seuil de diffusion d`un comportement}, bookTitle = {ESSA Conference, Model to Model workshop, Valladolid, ESP, 16-19/09/2004}, pages = {15}, url = {http://cemadoc.irstea.fr/cemoa/PUB00017647}, year = {2004}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, abstract = {We compare the individual-based "threshold model" of innovation diffusion in the version which has been studied by Young, with an aggregate model we derived from it. The classical threshold model supposes that an individual adopts a behaviour according to a trade-off between a social pressure and a personal interest. Our study considers only the case where all have the same threshold. We present an aggregated model, which takes into account variations of the neighbourhood sizes, whereas previous work assumed this size fixed. The comparison between the aggregated models (the first one assuming a neighbourhood size and the second one, a variable one) points out an improvement of the approximation in most of the value of parameter space. Remaining differences between both models give us some clues about the specific ability of individual-based model to maintain a minority behaviour which becomes a majority by an addition of stochastic effects. / Nous comparons un modèle individu-centré de diffusion de l`innovation (modèle à seuil) proposé par Young à ses approximations agrégées. Le classique modèle à seuil suppose qu`un individu adopte un comportement en fonction des valeurs relatives de la pression sociale qu`il subit et de son intérêt personnel pour ce comportement. Notre étude considère uniquement le cas où tous les individus ont même seuil. Nous présentons un modèle agrégé qui prend en compte la variation de la taille du voisinage d`un individu à l`autre alors que les précédents travaux supposait ce voisinage de taille constante pour tous les individus. La comparaison entre les modèles agrégés (un à voisinage de taille fixe, l`autre à voisinage de taille variable) montre une amélioration de l`approximation pour la plupart des valeurs de l`espace des paramètres. Les différences restantes entre les deux types de modèles nous fournissent quelques indicateurs sur les spécificités du modèle individu-centré, et notamment sur sa capacité à maintenir au sein de la population un comportement minoritaire qui peut, du fait de la stochasticité du modèle, devenir le comportement de la majorité.}, }
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F. Amblard, D.R. Hill, S. Bernard, J. Truffot, G. Deffuant
MDA compliant design of SimExplorer: a Software tool to handle simulation experimental framework
SCS International Summer Simulation Conference, Montréal, CAN, Juillet 2003 (p. 279-284), 2003
abs web bib

SimExplorer can manage the exploration and the execution of simulation experiments by means of experimental designs on several simulation models. This paper first discuss the need to handle experimental designs in a generic way. This leads to the proposition of a PIM for the management of simulation experiments following the MDA. And to illustrate the feasibility of our approach, we present design solutions to develop an efficient tool using XMI protocols between software components. Finally the implementation of a prototype is exposed. / SimExplorer peut gérer l'exploration et l'exécution d'expériences de simulation au moyen de plans d'expériences sur plusieurs modèles de simulation. Ce papier expose tout d'abord le besoin de contrôler les plans d'expérience de manière générique. Ce qui conduit à la proposition d'un PIM pour la gestion des expériences de simulation qui suit MDA. Et pour illustrer la faisabilité d'une telle approche, nous présentons des solutions de conception pour développer un outil efficace utilisant des protocoles XMI entre les composants logiciels. Enfin nous exposons l'implémentation d'un prototype.
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@inproceedings{PUB00011854, author = {Amblard, F. and Hill, D.R. and Bernard, S. and Truffot, J. and Deffuant, G.}, title = {MDA compliant design of SimExplorer: a Software tool to handle simulation experimental framework}, bookTitle = {SCS International Summer Simulation Conference, Montréal, CAN, Juillet 2003}, pages = {279-284}, url = {http://cemadoc.irstea.fr/cemoa/PUB00011854}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CNRS LIMOS UMR 6158 AUBIERE ; - ; - ; -}, number = {03/0319 ; K LI03 8}, abstract = {SimExplorer can manage the exploration and the execution of simulation experiments by means of experimental designs on several simulation models. This paper first discuss the need to handle experimental designs in a generic way. This leads to the proposition of a PIM for the management of simulation experiments following the MDA. And to illustrate the feasibility of our approach, we present design solutions to develop an efficient tool using XMI protocols between software components. Finally the implementation of a prototype is exposed. / SimExplorer peut gérer l'exploration et l'exécution d'expériences de simulation au moyen de plans d'expériences sur plusieurs modèles de simulation. Ce papier expose tout d'abord le besoin de contrôler les plans d'expérience de manière générique. Ce qui conduit à la proposition d'un PIM pour la gestion des expériences de simulation qui suit MDA. Et pour illustrer la faisabilité d'une telle approche, nous présentons des solutions de conception pour développer un outil efficace utilisant des protocoles XMI entre les composants logiciels. Enfin nous exposons l'implémentation d'un prototype.}, }
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F. Amblard, G. Deffuant, G. Weisbuch
Un niveau critique de connectivité du réseau social est nécessaire au basculement unanime vers une opinion extrême
Journées Graphes Réseaux et Modélisation, Paris, 17-18 décembre 2003 (p. 20-21), 2003
abs web bib

De nombreux modèles de dynamiques d'opinions reposent sur des opinions binaires ou discrètes que les individus du modèle mettent à jour en fonction de l'influence sociale qu'ils subissent. Une piste de recherche alternative porte sur les dynamiques d'une variable continue comme l'évaluation d'un choix (une utilité en économie par exemple) ou des croyances sur l'ajustement d'un paramètre de contrôle (un budget par exemple). Un modèle de dynamique de telles opinions continues a fait apparaître, dans certaines conditions, une dérive de l'ensemble de la population vers une des extrêmes, même lorque les extrêmistes initiaux sont répartis également sur les deux extrêmes. Ici est étudié l'influence du réseau social sur l'apparition de ce comportement dynamique.
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@inproceedings{PUB00014153, author = {Amblard, F. and Deffuant, G. and Weisbuch, G.}, title = {Un niveau critique de connectivité du réseau social est nécessaire au basculement unanime vers une opinion extrême}, title = {A critical level of social network connectivity is necessary to an unanimous shift to an extreme opinion}, bookTitle = {Journées Graphes Réseaux et Modélisation, Paris, 17-18 décembre 2003}, pages = {20-21}, url = {http://cemadoc.irstea.fr/cemoa/PUB00014153}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; ENS LPS}, number = {K LI03 11}, abstract = {De nombreux modèles de dynamiques d'opinions reposent sur des opinions binaires ou discrètes que les individus du modèle mettent à jour en fonction de l'influence sociale qu'ils subissent. Une piste de recherche alternative porte sur les dynamiques d'une variable continue comme l'évaluation d'un choix (une utilité en économie par exemple) ou des croyances sur l'ajustement d'un paramètre de contrôle (un budget par exemple). Un modèle de dynamique de telles opinions continues a fait apparaître, dans certaines conditions, une dérive de l'ensemble de la population vers une des extrêmes, même lorque les extrêmistes initiaux sont répartis également sur les deux extrêmes. Ici est étudié l'influence du réseau social sur l'apparition de ce comportement dynamique.}, }
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F. Amblard, G. Weisbuch, G. Deffuant
The drift to a single extreme appears only beyond a critical connectivity of the social networks
ESSA Conference, Groningen, NLD, Septembre 19-21 2003 (p. 12), 2003
abs web bib

In a first paragraph we present briefly the Relative Agreement Model, the addition of extremists within the population and the main results corresponding to the totally connected case. We then describe the first simulations done on a regular grid with a Von Neumann and a De Moore neighborhood. Significant changes occur in comparison with the totally connected case as for instance the disappearance of the single extreme convergence. Aiming at understanding it, we then explore the behavior of the model between regular grids and fully connected networks. We use a Small-World topology that enables us to tune both the average connectivity of the network and the level of noise within the network, from a regular network to a totally random one. The simulations show that there is a critical level of connectivity beyond which the drift to a single extreme appears. We then discuss the observed behavior of our model.
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@inproceedings{PUB00012076, author = {Amblard, F. and Weisbuch, G. and Deffuant, G.}, title = {The drift to a single extreme appears only beyond a critical connectivity of the social networks}, bookTitle = {ESSA Conference, Groningen, NLD, Septembre 19-21 2003}, pages = {12}, url = {http://cemadoc.irstea.fr/cemoa/PUB00012076}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; ENS LPS ; CEMAGREF CLERMONT FERRAND LICF}, number = {03/0470 ; K LI03 9-1 ; K LI03 9-2}, abstract = {In a first paragraph we present briefly the Relative Agreement Model, the addition of extremists within the population and the main results corresponding to the totally connected case. We then describe the first simulations done on a regular grid with a Von Neumann and a De Moore neighborhood. Significant changes occur in comparison with the totally connected case as for instance the disappearance of the single extreme convergence. Aiming at understanding it, we then explore the behavior of the model between regular grids and fully connected networks. We use a Small-World topology that enables us to tune both the average connectivity of the network and the level of noise within the network, from a regular network to a totally random one. The simulations show that there is a critical level of connectivity beyond which the drift to a single extreme appears. We then discuss the observed behavior of our model.}, }
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G. Deffuant, F. Amblard, G. Weisbuch, T. Faure
Comment une majorité modérée bascule-t-elle dans l'extrémisme ? Explication à partir du modèle d'attraction proportionnel à l'accord relatif
2ème Conférence Modèles Formels de l'Interaction, Lille, 20-22 mai 2003 (p. 71-80), 2003
abs web bib

We model opinion dynamics in populations of agents with continuous opinion and uncertainty. The opinions and uncertainties are modified by random pair interactions. We propose a new model of interactions, called relative agreement model, which is a variant of the previously discussed bounded confidence. In this model, uncertainty as well as opinion can be modified by interactions. We introduce extremist agents by attributing a much lower uncertainty (and thus higher persuasion) to a small proportion of agents at the extremes of the opinion distribution. We study the evolution of the opinion distribution submitted to the relative agreement model. Depending upon the choice of parameters, the extremists can have a very local influence or attract the whole population. We propose a qualitative analysis of the convergence process based on a local field notion. The genericity of the observed results is tested on several variants of the bounded confidence model. / Nous modélisons la dynamique des opinions d'une population d'agents ayant une opinion continue et une incertitude associée, en proposant un nouveau modèle d'interaction, le modèle d'accord relatif, qui est une variante des modèles de confiance limitée précédemment discutés. Dans ce modèle, l'incertitude ainsi que l'opinion peuvent être modifiées suite aux interactions aléatoires entre des paires d'agents. Nous introduisons des agents extrémistes dans la population en attribuant une incertitude très inférieure (et ainsi une force de persuasion plus élevée) à une proportion d'agents située aux extrémités de la distribution d'opinion. Nous étudions par la suite l'évolution de la distribution d'opinions. Suivant la valeur des paramètres, les extrémistes peuvent avoir une influence très locale ou au contraire attirer la population tout entière. Nous proposons une analyse qualitative du processus de convergence basée sur la notion de champ local.
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@inproceedings{PUB00011591, author = {Deffuant, G. and Amblard, F. and Weisbuch, G. and Faure, T.}, title = {Comment une majorité modérée bascule-t-elle dans l'extrémisme ? Explication à partir du modèle d'attraction proportionnel à l'accord relatif}, bookTitle = {2ème Conférence Modèles Formels de l'Interaction, Lille, 20-22 mai 2003}, pages = {71-80}, url = {http://cemadoc.irstea.fr/cemoa/PUB00011591}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; ECOLE NORMALE SUPERIEURE PARIS ; - ; -}, number = {03/0170 ; K LI03 7}, abstract = {We model opinion dynamics in populations of agents with continuous opinion and uncertainty. The opinions and uncertainties are modified by random pair interactions. We propose a new model of interactions, called relative agreement model, which is a variant of the previously discussed bounded confidence. In this model, uncertainty as well as opinion can be modified by interactions. We introduce extremist agents by attributing a much lower uncertainty (and thus higher persuasion) to a small proportion of agents at the extremes of the opinion distribution. We study the evolution of the opinion distribution submitted to the relative agreement model. Depending upon the choice of parameters, the extremists can have a very local influence or attract the whole population. We propose a qualitative analysis of the convergence process based on a local field notion. The genericity of the observed results is tested on several variants of the bounded confidence model. / Nous modélisons la dynamique des opinions d'une population d'agents ayant une opinion continue et une incertitude associée, en proposant un nouveau modèle d'interaction, le modèle d'accord relatif, qui est une variante des modèles de confiance limitée précédemment discutés. Dans ce modèle, l'incertitude ainsi que l'opinion peuvent être modifiées suite aux interactions aléatoires entre des paires d'agents. Nous introduisons des agents extrémistes dans la population en attribuant une incertitude très inférieure (et ainsi une force de persuasion plus élevée) à une proportion d'agents située aux extrémités de la distribution d'opinion. Nous étudions par la suite l'évolution de la distribution d'opinions. Suivant la valeur des paramètres, les extrémistes peuvent avoir une influence très locale ou au contraire attirer la population tout entière. Nous proposons une analyse qualitative du processus de convergence basée sur la notion de champ local.}, }
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G. Deffuant, F. Amblard, R. Duboz, E. Ramat
Une démarche expérimentale pour la simulation individus-centrée
10emes journées de Rochebrunes rencontres interdisciplinaires sur les systèmes complexes naturels et artificiels, Rochebrune, 26 Janvier au 6 Février 2003 (p. 45-64), 2003
abs web bib

We question ourselves about status of simulation considered as a a direct experimentation on computer model allowing to deepen knowledge about model functioning before represented phenomena... / Les interrogations sur le statut de la simulation sont souvent liées à la pertinence du lien entre le modèle et ce qu'il est censé représenter (Varenne 2001), et donc au crédit que l'on peut prêter aux résultats d'une simulation. Le problème est donc alors de rapprocher une simulation d'une expérimentation sur l'objet qu'elle représente, et de comparer les statuts de ces deux types d'expérimentations. Le remplacement d'essais de bombes nucléaires réelles par des simulations dans plusieurs pays par exemple pose légitimement ce type de questions.Nous nous plaçons cependant dans une perspective sensiblement différente : nous nous interrogeons sur le statut de la simulation en tant qu'expérimentation directe sur le modèle computationnel. Dans cette perspective, les simulations ont pour objectif premier de faire progresser la connaissance du fonctionnement du modèle, avant de faire progresser la connaissance du phénomène représenté.Une telle démarche peut probablement paraître choquante, au moins pour deux raisons. Tout d'abord, ne faisons-nous pas des modèles pour nous aider à comprendre des phénomènes que nous ne comprenons pas ? Alors quel intérêt d'y substituer des modèles que nous ne comprenons pas non plus (puisqu'il faut les étudier pour les comprendre) ? Mais, plus profondément, un modèle est totalement spécifié par son concepteur, donc les moindres mécanismes en sont connus. Comment se peut-il qu'il faille encore l'étudier pour le comprendre ?
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@inproceedings{PUB00011232, author = {Deffuant, G. and Amblard, F. and Duboz, R. and Ramat, E.}, title = {Une démarche expérimentale pour la simulation individus-centrée}, title = {An experimental step for individual-focused simulation}, bookTitle = {10emes journées de Rochebrunes rencontres interdisciplinaires sur les systèmes complexes naturels et artificiels, Rochebrune, 26 Janvier au 6 Février 2003}, pages = {45-64}, url = {http://cemadoc.irstea.fr/cemoa/PUB00011232}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; LABORATOIRE D'INFORMATIQUE DU LITTORAL CALAIS ; LABORATOIRE D'INFORMATIQUE DU LITTORAL CALAIS}, number = {03/0008 ; K LI03 2}, abstract = {We question ourselves about status of simulation considered as a a direct experimentation on computer model allowing to deepen knowledge about model functioning before represented phenomena... / Les interrogations sur le statut de la simulation sont souvent liées à la pertinence du lien entre le modèle et ce qu'il est censé représenter (Varenne 2001), et donc au crédit que l'on peut prêter aux résultats d'une simulation. Le problème est donc alors de rapprocher une simulation d'une expérimentation sur l'objet qu'elle représente, et de comparer les statuts de ces deux types d'expérimentations. Le remplacement d'essais de bombes nucléaires réelles par des simulations dans plusieurs pays par exemple pose légitimement ce type de questions.Nous nous plaçons cependant dans une perspective sensiblement différente : nous nous interrogeons sur le statut de la simulation en tant qu'expérimentation directe sur le modèle computationnel. Dans cette perspective, les simulations ont pour objectif premier de faire progresser la connaissance du fonctionnement du modèle, avant de faire progresser la connaissance du phénomène représenté.Une telle démarche peut probablement paraître choquante, au moins pour deux raisons. Tout d'abord, ne faisons-nous pas des modèles pour nous aider à comprendre des phénomènes que nous ne comprenons pas ? Alors quel intérêt d'y substituer des modèles que nous ne comprenons pas non plus (puisqu'il faut les étudier pour les comprendre) ? Mais, plus profondément, un modèle est totalement spécifié par son concepteur, donc les moindres mécanismes en sont connus. Comment se peut-il qu'il faille encore l'étudier pour le comprendre ?}, }
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R. Duboz, F. Amblard, E. Ramat, G. Deffuant, P. Preux
Individual-based model to enrich an aggregate model
Workshop M2M, Marseille, 31 Mars-1er Avril 2003 (p. 57-64), 2003
abs web bib

We propose to use individual-based models as virtual laboratories to identify parameters of aggregate models. We illustrate this approach with a simple example: the diffusion of particles animated by a Brownian movement. We thus have an aggregated numerical model, as well as an individual-based model of this process. We then use the individual-based model as a virtual laboratory. In particular, we consider the coupling between both models in which the aggregate model asks for computations of parameters to the individual-based model. Finally, we evoke the case of scale shifts in the models and the way it can be handled by this type of approach. / Nous proposons d'utiliser des modèles individus-centrés comme des laboratoires virtuels pour identifier les paramètres de modèles agrégés. Nous illustrons l'approche avec un exemple simple : la diffusion de particules animées d'un mouvement brownien. Nous avons dans ce cas un modèle numérique agrégé ainsi qu'un modèle individu-centré du processus. Nous utilisons alors le modèle individu-centré comme un laboratoire virtuel. En particulier, nous considérons le couplage entre les deux modèles, pour lequel le modèle agrégé demande le calcul des paramètres au modèle individu-centré. Finalement, nous évoquons le cas du changement d'échelles dans les modèles et la manière de le gérer par ce type d'approche.
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@inproceedings{PUB00011596, author = {Duboz, R. and Amblard, F. and Ramat, E. and Deffuant, G. and Preux, P.}, title = {Individual-based model to enrich an aggregate model}, title = {Un modèle individu-centré utilisé pour enrichir un modèle agrégé}, bookTitle = {Workshop M2M, Marseille, 31 Mars-1er Avril 2003}, pages = {57-64}, url = {http://cemadoc.irstea.fr/cemoa/PUB00011596}, year = {2003}, affiliation = {LABORATOIRE D'INFORMATIQUE DU LITTORAL CALAIS ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, number = {03/0172 ; K LI03 5}, abstract = {We propose to use individual-based models as virtual laboratories to identify parameters of aggregate models. We illustrate this approach with a simple example: the diffusion of particles animated by a Brownian movement. We thus have an aggregated numerical model, as well as an individual-based model of this process. We then use the individual-based model as a virtual laboratory. In particular, we consider the coupling between both models in which the aggregate model asks for computations of parameters to the individual-based model. Finally, we evoke the case of scale shifts in the models and the way it can be handled by this type of approach. / Nous proposons d'utiliser des modèles individus-centrés comme des laboratoires virtuels pour identifier les paramètres de modèles agrégés. Nous illustrons l'approche avec un exemple simple : la diffusion de particules animées d'un mouvement brownien. Nous avons dans ce cas un modèle numérique agrégé ainsi qu'un modèle individu-centré du processus. Nous utilisons alors le modèle individu-centré comme un laboratoire virtuel. En particulier, nous considérons le couplage entre les deux modèles, pour lequel le modèle agrégé demande le calcul des paramètres au modèle individu-centré. Finalement, nous évoquons le cas du changement d'échelles dans les modèles et la manière de le gérer par ce type d'approche.}, }
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R. Duboz, E. Ramat, P. Preux, F. Amblard, G. Deffuant
Utiliser les modèles individus-centrés comme laboratoires virtuels pour identifier les paramètres d'un modèle agrégé
4ème conférence francophone de Modélisation et Simulation MOSIM'03, Toulouse, 23-25 avril 2003 (p. 353-357), 2003
abs web bib

We propose to use individual-based models as virtual laboratories to identify parameters of aggregate models. We illustrate this approach with a simple example: the diffusion of particles animated by a Brownian movement. We thus have an aggregated numerical model, as well as an individual-based model of this process. We then use the individual-based model as a virtual laboratory. In particular, we consider the coupling between both models in which the aggregate model asks for computations of parameters to the individual-based model. Finally, we evoke the case of scale shifts in the models and the way it can be handled by this type of approach. / Nous proposons d'utiliser des modèles individus-centrés comme des laboratoires virtuels pour identifier les paramètres de modèles agrégés. Nous illustrons l'approche avec un exemple simple : la diffusion de particules animées d'un mouvement brownien. Nous avons dans ce cas un modèle numérique agrégé ainsi qu'un modèle individu-centré du processus. Nous utilisons alors le modèle individu-centré comme un laboratoire virtuel. En particulier, nous considérons le couplage entre les deux modèles, pour lequel le modèle agrégé demande le calcul des paramètres au modèle individu-centré. Finalement, nous évoquons le cas du changement d'échelles dans les modèles et la manière de le gérer par ce type d'approche.
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@inproceedings{PUB00011597, author = {Duboz, R. and Ramat, E. and Preux, P. and Amblard, F. and Deffuant, G.}, title = {Utiliser les modèles individus-centrés comme laboratoires virtuels pour identifier les paramètres d'un modèle agrégé}, title = {Individual-based model to enrich an aggregate model}, bookTitle = {4ème conférence francophone de Modélisation et Simulation MOSIM'03, Toulouse, 23-25 avril 2003}, pages = {353-357}, url = {http://cemadoc.irstea.fr/cemoa/PUB00011597}, year = {2003}, affiliation = {LABORATOIRE D'INFORMATIQUE DU LITTORAL CALAIS ; CEMAGREF CLERMONT FERRAND LICF ; - ; - ; -}, number = {03/0173}, abstract = {We propose to use individual-based models as virtual laboratories to identify parameters of aggregate models. We illustrate this approach with a simple example: the diffusion of particles animated by a Brownian movement. We thus have an aggregated numerical model, as well as an individual-based model of this process. We then use the individual-based model as a virtual laboratory. In particular, we consider the coupling between both models in which the aggregate model asks for computations of parameters to the individual-based model. Finally, we evoke the case of scale shifts in the models and the way it can be handled by this type of approach. / Nous proposons d'utiliser des modèles individus-centrés comme des laboratoires virtuels pour identifier les paramètres de modèles agrégés. Nous illustrons l'approche avec un exemple simple : la diffusion de particules animées d'un mouvement brownien. Nous avons dans ce cas un modèle numérique agrégé ainsi qu'un modèle individu-centré du processus. Nous utilisons alors le modèle individu-centré comme un laboratoire virtuel. En particulier, nous considérons le couplage entre les deux modèles, pour lequel le modèle agrégé demande le calcul des paramètres au modèle individu-centré. Finalement, nous évoquons le cas du changement d'échelles dans les modèles et la manière de le gérer par ce type d'approche.}, }
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M. Edwards, S. Huet, F. Goreaud, G. Deffuant
Comparing individual-based model of behaviour diffusion with its mean field aggregated approximation
Model to model (M2M), Marseille, 31 mars et 1er avril 2003 (p. 12), 2003
abs web bib

We compare the individual-based "threshold model"of innovation diffusion (Valente 1995), in the version which has been studied by P. Young, and an aggregate deterministic model we constructed from it. The classical threshold model supposes that an individual adopts a behaviour according to a trade-off between a social pressure (the number of neighbours adopting the behaviour) and a personal interest or resistance to change (the threshold). The aggregate model makes approximations in order to estimate the evolution of groups of individuals with the same number of neighbours of similar behaviour. We compare both models in different points of the parameter space. We find that the aggregate model gives a good approximation of the indicidual in some cases ; however, in other cases the behaviour of the aggregate approximations differs. Using theoretical interpretation of this difference based on a study of the attractors of the aggregate model, we hypothesed that the two models have the same behaviour when the aggregate model has only one attractor and that differences can occur when it has two. / Nous comparons un modèle individu-centré à seuil de diffusion de l'innovation (Valente 1995) dans la version étudiée par P. Young, et un modèle agrégé déterministe que nous avons construit en cohérence. Le modèle classique de diffusion de l'innovation à seuil suppose qu'un individu adopte un comportement suivant un compromis entre la pression sociale (le nombre de ses voisins ayant adopté ce comportement) et un intérêt personnel de résistance au changement (le seuil). Le modèle agrégé fait appel à des approximations pour estimer l'évolution de groupes d'individus ayant le même nombre de voisins suivant un certain comportement. Nous comparons ces deux modèles en différents points de l'espace des paramètres. Nous trouvons que le modèle agrégé approxime bien le modèle individu-centré dans certains cas ; toutefois, il s'avère également parfois que le comportement du modèle agrégé diffère. En nous appuyant sur une interprétation théorique de cette différence, fondée sur une étude des attracteurs du modèle agrégé, nous proposons l'hypothèse que les deux modèles suivent le même comportement lorsque le modèle agrégé n'a qu'un seul attracteur, et que des différences peuvent apparaître quand il en a deux.
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@inproceedings{PUB00011529, author = {Edwards, M. and Huet, S. and Goreaud, F. and Deffuant, G.}, title = {Comparing individual-based model of behaviour diffusion with its mean field aggregated approximation}, title = {Comparaison d'un modèle individu-centré de diffusion de l'innovation avec son approximation par champ moyen}, bookTitle = {Model to model (M2M), Marseille, 31 mars et 1er avril 2003}, pages = {12}, url = {http://cemadoc.irstea.fr/cemoa/PUB00011529}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, number = {03/0088 ; K LI03 3}, abstract = {We compare the individual-based "threshold model"of innovation diffusion (Valente 1995), in the version which has been studied by P. Young, and an aggregate deterministic model we constructed from it. The classical threshold model supposes that an individual adopts a behaviour according to a trade-off between a social pressure (the number of neighbours adopting the behaviour) and a personal interest or resistance to change (the threshold). The aggregate model makes approximations in order to estimate the evolution of groups of individuals with the same number of neighbours of similar behaviour. We compare both models in different points of the parameter space. We find that the aggregate model gives a good approximation of the indicidual in some cases ; however, in other cases the behaviour of the aggregate approximations differs. Using theoretical interpretation of this difference based on a study of the attractors of the aggregate model, we hypothesed that the two models have the same behaviour when the aggregate model has only one attractor and that differences can occur when it has two. / Nous comparons un modèle individu-centré à seuil de diffusion de l'innovation (Valente 1995) dans la version étudiée par P. Young, et un modèle agrégé déterministe que nous avons construit en cohérence. Le modèle classique de diffusion de l'innovation à seuil suppose qu'un individu adopte un comportement suivant un compromis entre la pression sociale (le nombre de ses voisins ayant adopté ce comportement) et un intérêt personnel de résistance au changement (le seuil). Le modèle agrégé fait appel à des approximations pour estimer l'évolution de groupes d'individus ayant le même nombre de voisins suivant un certain comportement. Nous comparons ces deux modèles en différents points de l'espace des paramètres. Nous trouvons que le modèle agrégé approxime bien le modèle individu-centré dans certains cas ; toutefois, il s'avère également parfois que le comportement du modèle agrégé diffère. En nous appuyant sur une interprétation théorique de cette différence, fondée sur une étude des attracteurs du modèle agrégé, nous proposons l'hypothèse que les deux modèles suivent le même comportement lorsque le modèle agrégé n'a qu'un seul attracteur, et que des différences peuvent apparaître quand il en a deux.}, }
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M. Edwards, S. Huet, F. Goreaud, G. Deffuant
Comparing an innovation diffusion IBM and its aggregated version derived by mean field approximation for short term simulations
Modèles formels de l'interaction (MFI03), Lille, 20-22 mai 2003 (p. 11), 2003
abs web bib

We compare two models at short term (200 time steps) models. On the one hand, a stochastic individual based model of innovation diffusion (Valente 1995) inspired from the game theory, in which the probability for an individual to make the choice suggested by the social pressure follows a Gibb's function, whose asymptotic behaviour has been described in (Young, 1999). On the other hand, a deterministic aggregate model which we derive from the previous one by considering an average network and following a mean field approximation.For a particular zone in the parameter space, which we studied and where the aggregated model has two equilibrium points, there exist differences between the two models at short term and they are located around the limit between two attractions basins existing for the aggrgated model. When aggregated model has only one equilibrium point, the two models are equivalent. / Nous utilisons un modèle de diffusion de l'innovation (Valente 1995) pour lequel la probabilité d'un individu d'opter pour le choix suggéré par la pression sociale suit une fonction de Gibbs. Ce modèle individu-centré stochastique, dont Young (1999) a étudié et décrit le comportement asymptotique, est comparé à un modèle agrégé déterministe dérivé du modèle individu-centré par une approche de type champ moyen. Nous écrivons l'équation maîtresse régissant l'évolution des probabilités des différentes configurations de ce réseau moyen et déterminons la part de chacun des comportements dans la population. Pour un sous-ensemble de paramètres étudiés, des différences entre ces deux modèles existent et se situent autour de la limite du bassin d'attraction du modèle agrégé lorsque celui-ci est doté de deux points d'équilibre stable. Ces différences apparaissent à court terme. Par ailleurs, lorsque le modèle agrégé n'a qu'un point d'équilibre, il n'y a aucune différence entre les deux modèles.
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@inproceedings{PUB00011530, author = {Edwards, M. and Huet, S. and Goreaud, F. and Deffuant, G.}, title = {Comparing an innovation diffusion IBM and its aggregated version derived by mean field approximation for short term simulations}, title = {Comparaison entre un modèle individu-centré de diffusion et sa version agrégée dérivée par champ moyen pour des simulations à court terme}, bookTitle = {Modèles formels de l'interaction (MFI03), Lille, 20-22 mai 2003}, pages = {11}, url = {http://cemadoc.irstea.fr/cemoa/PUB00011530}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, number = {03/0089 ; K LI03 4}, abstract = {We compare two models at short term (200 time steps) models. On the one hand, a stochastic individual based model of innovation diffusion (Valente 1995) inspired from the game theory, in which the probability for an individual to make the choice suggested by the social pressure follows a Gibb's function, whose asymptotic behaviour has been described in (Young, 1999). On the other hand, a deterministic aggregate model which we derive from the previous one by considering an average network and following a mean field approximation.For a particular zone in the parameter space, which we studied and where the aggregated model has two equilibrium points, there exist differences between the two models at short term and they are located around the limit between two attractions basins existing for the aggrgated model. When aggregated model has only one equilibrium point, the two models are equivalent. / Nous utilisons un modèle de diffusion de l'innovation (Valente 1995) pour lequel la probabilité d'un individu d'opter pour le choix suggéré par la pression sociale suit une fonction de Gibbs. Ce modèle individu-centré stochastique, dont Young (1999) a étudié et décrit le comportement asymptotique, est comparé à un modèle agrégé déterministe dérivé du modèle individu-centré par une approche de type champ moyen. Nous écrivons l'équation maîtresse régissant l'évolution des probabilités des différentes configurations de ce réseau moyen et déterminons la part de chacun des comportements dans la population. Pour un sous-ensemble de paramètres étudiés, des différences entre ces deux modèles existent et se situent autour de la limite du bassin d'attraction du modèle agrégé lorsque celui-ci est doté de deux points d'équilibre stable. Ces différences apparaissent à court terme. Par ailleurs, lorsque le modèle agrégé n'a qu'un point d'équilibre, il n'y a aucune différence entre les deux modèles.}, }
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G. Deffuant, F. Amblard, T. Faure, G. Weisbuch
Interacting Agents with Continuous Uncertain Opinions
Workshop on Economics with Heterogeneous Interacting Agents, Maastricht, NLD, june 2001 , 2001
abs web bib

We present several possible extensions of a model of opinion dynamics in which each agent adjusts a continuous opinion as a result of an interaction with a randomly chosen other agent whenever the difference between their opinions is below a given threshold. In this first model, high thresholds yield convergence of all opinions towards the average opinion, whereas low thresholds result in several opinion clusters. We then focus on a particular case where the threshold can take two values: a low and high one. If the thresholds remain constant, different clustering time scales are observed: on the long run clustering depends on the higher threshold. If we interpret the threshold as an uncertainty of the opinion, we define dynamics of influence on the uncertainty as well as on the opinions when agents interact. In this case, opinion clustering is driven by threshold dynamics. In particular, we study the case where confident (low uncertainty) agents have more influence and are located at the extremes of the distribution (the extremists). We study the parameter values for which the extremists are dominant and lead to the constitution of two opposite clusters by attracting all the moderate agents. / Nous présentons plusieurs extensions possibles d'un modèle de dynamique d'opinion dans lequel chaque agent ajuste une opinion continue en fonction d'interaction avec d'autres agents choisis aléatoirement quand la différence entre leur opinions est en-dessous d'un certain seuil. Dans ce premier modèle, les seuils élevés conduise à une convergence des opinions vers une opinions moyenne, alors que les seuils faibles résultent en plusieurs groupes d'opinions. Nous nous intéressons alors au cas particulier où le seuil peut prendre deux valeurs : une basse et une haute. Si nous interprétons le seuil en terme d'incertitude de l'opinion, nous définissons une dynamique d'influence sur l'incertitude ainsi que sur l'opinion lors des interactions. Dans ce cas, le regroupement des opinions est conduit par la dynamique des seuils. En particulier, nous étudions le cas où des agents certains (de faible incertitude) ont plus d'influence et sont localisés aux extrémités de la distribution (les extrémistes). Nous étudions les valeurs de ce paramètre pour lesquelles les extrémistes sont dominants et conduisent à la constitution de deux groupes opposés en attirant tous les agents modérés.
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@inproceedings{PUB00009124, author = {Deffuant, G. and Amblard, F. and Faure, T. and Weisbuch, G.}, title = {Interacting Agents with Continuous Uncertain Opinions}, title = {Agents en interaction et dynamique d'opinions continues}, bookTitle = {Workshop on Economics with Heterogeneous Interacting Agents, Maastricht, NLD, june 2001}, url = {http://cemadoc.irstea.fr/cemoa/PUB00009124}, year = {2001}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; ECOLE NORMALE SUPERIEURE LABORATOIRE DE PHYSIQUE STATISTIQUE PARIS ; - ; -}, number = {01/0113 ; K LI01 6}, abstract = {We present several possible extensions of a model of opinion dynamics in which each agent adjusts a continuous opinion as a result of an interaction with a randomly chosen other agent whenever the difference between their opinions is below a given threshold. In this first model, high thresholds yield convergence of all opinions towards the average opinion, whereas low thresholds result in several opinion clusters. We then focus on a particular case where the threshold can take two values: a low and high one. If the thresholds remain constant, different clustering time scales are observed: on the long run clustering depends on the higher threshold. If we interpret the threshold as an uncertainty of the opinion, we define dynamics of influence on the uncertainty as well as on the opinions when agents interact. In this case, opinion clustering is driven by threshold dynamics. In particular, we study the case where confident (low uncertainty) agents have more influence and are located at the extremes of the distribution (the extremists). We study the parameter values for which the extremists are dominant and lead to the constitution of two opposite clusters by attracting all the moderate agents. / Nous présentons plusieurs extensions possibles d'un modèle de dynamique d'opinion dans lequel chaque agent ajuste une opinion continue en fonction d'interaction avec d'autres agents choisis aléatoirement quand la différence entre leur opinions est en-dessous d'un certain seuil. Dans ce premier modèle, les seuils élevés conduise à une convergence des opinions vers une opinions moyenne, alors que les seuils faibles résultent en plusieurs groupes d'opinions. Nous nous intéressons alors au cas particulier où le seuil peut prendre deux valeurs : une basse et une haute. Si nous interprétons le seuil en terme d'incertitude de l'opinion, nous définissons une dynamique d'influence sur l'incertitude ainsi que sur l'opinion lors des interactions. Dans ce cas, le regroupement des opinions est conduit par la dynamique des seuils. En particulier, nous étudions le cas où des agents certains (de faible incertitude) ont plus d'influence et sont localisés aux extrémités de la distribution (les extrémistes). Nous étudions les valeurs de ce paramètre pour lesquelles les extrémistes sont dominants et conduisent à la constitution de deux groupes opposés en attirant tous les agents modérés.}, }
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P. Eynard, M. Mas, A. Penciolelli, C. Tinet, G. Deffuant
Contamination of meat, and exposure of abattoir workers, by CNS material during standard butchering processes prevalent in the member states of the European Union (EUCNSRISK)
FAIR-CT98-7004 2nd progress report, Clermont-Ferrand, 22 octobre 2001 (p. 34), 2001
abs web bib

A stochastic model of the dissemination of central nervous system (CNS) proteins during slaughtering and butchering operations has been developed. Inputs to this model include results from an investigation about slaughtering techniques prevalent in the European Union, and measures of specific CNS proteins on 576 carcasses in seven countries within the EU. The model provides estimates of infectivity in various outputs of the abattoirs. A number of scenario are compared. The study of the sensitivity of the model provides a ranking of the existing preventive measures. / Un modèle de stochastique de la dissémination des protéines du système nerveux central (SNC) des bovins au cours des opérations d'abattage et de découpe a été développé. Ce modèle prend en compte les résultats d'une enquête sur les pratiques d'abattage en vigueur dans l'Union Européenne, ainsi que des mesures de concentration de protéines spécifiques du SNC réalisées sur 576 carcasses dans 7 pays de l'UE. Le modèle fournit une estimation de l'infectiosité présente dans différents produits de l'abattage. Plusieurs scénarios sont comparés. L'étude de la sensibilité du modèle fournit un classement des mesures de maîtrise du risque.
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@inproceedings{PUB00009964, author = {Eynard, P. and Mas, M. and Penciolelli, A. and Tinet, C. and Deffuant, G.}, title = {Contamination of meat, and exposure of abattoir workers, by CNS material during standard butchering processes prevalent in the member states of the European Union (EUCNSRISK)}, title = {Contamination de la viande et exposition des travailleurs à l'abatoir par le matériel du système nerveux central lorsqu'ils procèdent à des activités standards de boucherie répandues dans les états membres de l'Union Européenne (EUCNSRISK)}, bookTitle = {FAIR-CT98-7004 2nd progress report, Clermont-Ferrand, 22 octobre 2001}, pages = {34}, url = {http://cemadoc.irstea.fr/cemoa/PUB00009964}, year = {2001}, affiliation = {CEMAGREF CLERMONT FERRAND UR TSCF FRA ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF MONTPELLIER GEMO ; - ; -}, number = {01/0657 ; K TS01 14}, abstract = {A stochastic model of the dissemination of central nervous system (CNS) proteins during slaughtering and butchering operations has been developed. Inputs to this model include results from an investigation about slaughtering techniques prevalent in the European Union, and measures of specific CNS proteins on 576 carcasses in seven countries within the EU. The model provides estimates of infectivity in various outputs of the abattoirs. A number of scenario are compared. The study of the sensitivity of the model provides a ranking of the existing preventive measures. / Un modèle de stochastique de la dissémination des protéines du système nerveux central (SNC) des bovins au cours des opérations d'abattage et de découpe a été développé. Ce modèle prend en compte les résultats d'une enquête sur les pratiques d'abattage en vigueur dans l'Union Européenne, ainsi que des mesures de concentration de protéines spécifiques du SNC réalisées sur 576 carcasses dans 7 pays de l'UE. Le modèle fournit une estimation de l'infectiosité présente dans différents produits de l'abattage. Plusieurs scénarios sont comparés. L'étude de la sensibilité du modèle fournit un classement des mesures de maîtrise du risque.}, }
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G. Deffuant, N. Ferrand, F. Amblard, N. Gilbert, G. Weisbuch
A model of Decision process mixing rational anticipation and social influences: example of agri-environmental measure adoption by farmers
Computational analysis of social and organizational system international conference, Pittsburgh, USA, July 2000 (p. 4), 2000
abs web bib

A model of the decision process mixing rational anticipation and social influences is proposed to study the dynamics of agri-environmental measure adoption by farmers in Breadalbane ESA. The decisions of the farmers are based on uncertain anticipations related to different criteria (revenue, independence, nature). These anticipations can be the result of a rational evaluation or a feeling or impression gathered from interactions with other farmers and institutional actors. The model simulates emissions and receptions of messages about these anticipations. Different states of the decision are defined, taking into account the anticipations and the motivations of the farmers. The model is linked to different sources of data : interviews with farmers and institutional actors and data on the population of farms. The different parameters are fitted with the data of participation to ESA meetings and ESA adoption. / Un modèle du processus de décision agrégeant anticipation rationnelle et influences sociales est proposé pour étudier la dynamique d'adoption des mesures agri-environnementales par les agriculteurs de Breadalbane. Les décisions des agriculteurs sont basées sur des anticipations incertaines relatives à différents critères (revenu, indépendance, environnement). Ces anticipations peuvent résulter d'une évaluation rationnelle ou d'un sentiment ou d'une impression issues d'interactions avec les autres agriculteurs et acteurs institutionnels. Le modèle simule les émissions et réceptions de messages à propos de ces anticipations. Différents états de décision sont définis, prenant en compte les anticipations et les motivations des agriculteurs. Le modèle est lié à différentes sources de données : enquêtes auprès des agriculteurs et des acteurs institutionnels et données sur la population des exploitations. Les différents paramètres sont ajustés aux données de participation aux réunions de l'ESA et à l'adoption de l'ESA.
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@inproceedings{PUB00009185, author = {Deffuant, G. and Ferrand, N. and Amblard, F. and Gilbert, N. and Weisbuch, G.}, title = {A model of Decision process mixing rational anticipation and social influences: example of agri-environmental measure adoption by farmers}, title = {Modèle du processus de décision agrégeant anticipation rationnelle et influences sociales : exemple de l'adoption de mesures agri-environementales par les agriculteurs}, bookTitle = {Computational analysis of social and organizational system international conference, Pittsburgh, USA, July 2000}, pages = {4}, url = {http://cemadoc.irstea.fr/cemoa/PUB00009185}, year = {2000}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; UNIVERSITY OF SURREY GUILDBORD GBR ; ECOLE NORMALE SUPERIEURE PARIS ; - ; -}, number = {00/0800}, abstract = {A model of the decision process mixing rational anticipation and social influences is proposed to study the dynamics of agri-environmental measure adoption by farmers in Breadalbane ESA. The decisions of the farmers are based on uncertain anticipations related to different criteria (revenue, independence, nature). These anticipations can be the result of a rational evaluation or a feeling or impression gathered from interactions with other farmers and institutional actors. The model simulates emissions and receptions of messages about these anticipations. Different states of the decision are defined, taking into account the anticipations and the motivations of the farmers. The model is linked to different sources of data : interviews with farmers and institutional actors and data on the population of farms. The different parameters are fitted with the data of participation to ESA meetings and ESA adoption. / Un modèle du processus de décision agrégeant anticipation rationnelle et influences sociales est proposé pour étudier la dynamique d'adoption des mesures agri-environnementales par les agriculteurs de Breadalbane. Les décisions des agriculteurs sont basées sur des anticipations incertaines relatives à différents critères (revenu, indépendance, environnement). Ces anticipations peuvent résulter d'une évaluation rationnelle ou d'un sentiment ou d'une impression issues d'interactions avec les autres agriculteurs et acteurs institutionnels. Le modèle simule les émissions et réceptions de messages à propos de ces anticipations. Différents états de décision sont définis, prenant en compte les anticipations et les motivations des agriculteurs. Le modèle est lié à différentes sources de données : enquêtes auprès des agriculteurs et des acteurs institutionnels et données sur la population des exploitations. Les différents paramètres sont ajustés aux données de participation aux réunions de l'ESA et à l'adoption de l'ESA.}, }
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G. Deffuant, S. Skerratt, F. Amblard, N. Ferrand, E. Chattoe, N. Gilbert, G. Weisbuch
Agent-based simulation of decision process mixing rational reasoning and influences from socio-informational networks : case studies of agri-environmental measures adoption by farmers
5th internationale conference on social science methodology, Cologne, DEU, October 2000 (p. 16), 2000
abs web bib

A model of the decision process mixing rational anticipation and social influences is proposed to study the dynamics of agri-environmental measure adoption by farmers in Breadalbane ESA. The decisions of the farmers are based on uncertain anticipations related to different criteria (revenue, independence, nature). These anticipations can be the result of a rational evaluation or a feeling or impression gathered from interactions with other farmers and institutional actors. The model simulates emissions and receptions of messages about these anticipations. Different states of the decision are defined, taking into account the anticipations and the motivations of the farmers. The model is linked to different sources of data : interviews with farmers and institutional actors and data on the population of farms. The different parameters are fitted with the data of participation to ESA meetings and ESA adoption. / Un modèle du processus de décision agrégeant anticipation rationnelle et influences sociales est proposé pour étudier la dynamique d'adoption des mesures agri-environnementales par les agriculteurs de Breadalbane. Les décisions des agriculteurs sont basées sur des anticipations incertaines relatives à différents critères (revenu, indépendance, environnement). Ces anticipations peuvent résulter d'une évaluation rationnelle ou d'un sentiment ou d'une impression issues d'interactions avec les autres agriculteurs et acteurs institutionnels. Le modèle simule les émissions et réceptions de messages à propos de ces anticipations. Différents états de décision sont définis, prenant en compte les anticipations et les motivations des agriculteurs. Le modèle est lié à différentes sources de données : enquêtes auprès des agriculteurs et des acteurs institutionnels et données sur la population des exploitations. Les différents paramètres sont ajustés aux données de participation aux réunions de l'ESA et à l'adoption de l'ESA.
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@inproceedings{PUB00009186, author = {Deffuant, G. and Skerratt, S. and Amblard, F. and Ferrand, N. and Chattoe, E. and Gilbert, N. and Weisbuch, G.}, title = {Agent-based simulation of decision process mixing rational reasoning and influences from socio-informational networks : case studies of agri-environmental measures adoption by farmers}, title = {Simulation individu-centrée du processus de décision agrégeant raisonnement rationnel et influences des réseaux socio-informationnels : Etude de cas de l'adoption de mesures agri-environnementales par les agriculteurs}, bookTitle = {5th internationale conference on social science methodology, Cologne, DEU, October 2000}, pages = {16}, url = {http://cemadoc.irstea.fr/cemoa/PUB00009186}, year = {2000}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; UNIVERSITY OF SURREY GUILDBORD GBR ; ECOLE NORMALE SUPERIEURE PARIS ; ROYAL AGRICULTURAL COLLEGE CIRENCESTER GBR ; - ; - ; -}, number = {00/0801}, abstract = {A model of the decision process mixing rational anticipation and social influences is proposed to study the dynamics of agri-environmental measure adoption by farmers in Breadalbane ESA. The decisions of the farmers are based on uncertain anticipations related to different criteria (revenue, independence, nature). These anticipations can be the result of a rational evaluation or a feeling or impression gathered from interactions with other farmers and institutional actors. The model simulates emissions and receptions of messages about these anticipations. Different states of the decision are defined, taking into account the anticipations and the motivations of the farmers. The model is linked to different sources of data : interviews with farmers and institutional actors and data on the population of farms. The different parameters are fitted with the data of participation to ESA meetings and ESA adoption. / Un modèle du processus de décision agrégeant anticipation rationnelle et influences sociales est proposé pour étudier la dynamique d'adoption des mesures agri-environnementales par les agriculteurs de Breadalbane. Les décisions des agriculteurs sont basées sur des anticipations incertaines relatives à différents critères (revenu, indépendance, environnement). Ces anticipations peuvent résulter d'une évaluation rationnelle ou d'un sentiment ou d'une impression issues d'interactions avec les autres agriculteurs et acteurs institutionnels. Le modèle simule les émissions et réceptions de messages à propos de ces anticipations. Différents états de décision sont définis, prenant en compte les anticipations et les motivations des agriculteurs. Le modèle est lié à différentes sources de données : enquêtes auprès des agriculteurs et des acteurs institutionnels et données sur la population des exploitations. Les différents paramètres sont ajustés aux données de participation aux réunions de l'ESA et à l'adoption de l'ESA.}, }
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G. Deffuant, D. Neau, F. Amblard, G. Weisbuch
Mixing beliefs among interacting agents
2nd international conference on computer simulations and the social sciences, Paris, september 2000 (p. 87-98), 2000
abs web bib

We present a model of opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. High thresholds yield convergence of opinions towards an average opinion, whereas low thresholds result in several opinion clusters: members of the ame cluster share the same opinion but are no longer influenced by members of other clusters. / Nous présentons un modèle de dynamique des opinions dans lequel les agents ajustent des opinions continues en fonction de rencontres binaires aléatoires, lorsque la différence entre leurs opinions est en-dessous d'un certain seuil. Les seuils hauts conduisent à une convergence des opinions vers une opinions moyenne, alors que les seuils plus bas conduisent à plusieurs agglomérats d'opinion : les membres d'un même agglomérat partageant la même opinion mais n'étant plus influencés par les membres d'autres agglomérats.
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@inproceedings{PUB00008486, author = {Deffuant, G. and Neau, D. and Amblard, F. and Weisbuch, G.}, title = {Mixing beliefs among interacting agents}, title = {Evolution des croyances entre agents en interactions}, bookTitle = {2nd international conference on computer simulations and the social sciences, Paris, september 2000}, pages = {87-98}, url = {http://cemadoc.irstea.fr/cemoa/PUB00008486}, year = {2000}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; ECOLE NORMALE SUPERIEURE LABORATOIRE DE PHYSIQUE STATISTIQUE PARIS ; - ; -}, number = {00/0399 ; K IAS 11}, abstract = {We present a model of opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. High thresholds yield convergence of opinions towards an average opinion, whereas low thresholds result in several opinion clusters: members of the ame cluster share the same opinion but are no longer influenced by members of other clusters. / Nous présentons un modèle de dynamique des opinions dans lequel les agents ajustent des opinions continues en fonction de rencontres binaires aléatoires, lorsque la différence entre leurs opinions est en-dessous d'un certain seuil. Les seuils hauts conduisent à une convergence des opinions vers une opinions moyenne, alors que les seuils plus bas conduisent à plusieurs agglomérats d'opinion : les membres d'un même agglomérat partageant la même opinion mais n'étant plus influencés par les membres d'autres agglomérats.}, }
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P. Eynard, M. Mas, C. Tinet, S. Bernard, G. Deffuant
Modelling and Evaluation of a Risk Management System Case of the BSE Hazard in the Slaughtering Process
FOOD'SIM 2000 1st International Conference on Simulation in Food and Bio-industries, Nantes, 26-27 juin 2000 (p. 277-283), 2000
abs web bib

A probabilistic model of risk evaluation in a slaughterhouse is proposed. The aim of the model is to offer the possibility to test different scenarios of preventive measures application. The model is based on: an expert analysis of processes and materials flow in various slaughterhouses a quantification of the BSE risk in terms of infectious doses possibly contained by the materials an evaluation of the probability that a set of preventive measures having an effect on the materials flow is applied. The outputs of the model are numbers of doses at the end of the different pathways of the process and the corresponding probabilities, if an infected animal is slaughtered. / Un modèle probabiliste de l'évaluation du risque dans un abattoir est proposé. L'objectif de la modélisation est de permettre de tester différents scénarios d'application des mesures de maîtrise du risque. Le modèle est fondé sur : l'analyse par des experts du procédé d'abattage et des flux de matières dans différents abattoirs, une quantification du risque ESB en termes de doses infectieuses potentiellement contenues dans les matières, une évaluation de la probabilité qu'un ensemble de mesures de maîtrise, ayant un effet sur les flux de matières, soit effectivement appliqué. Le procédé est ainsi représenté par un graphe. Les sorties du modèle sont les nombres de doses correspondant, dans les cas ou un animal infecté serait abattu, aux différents chemins du graphe et les probabilités correspondantes.
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@inproceedings{PUB00008303, author = {Eynard, P. and Mas, M. and Tinet, C. and Bernard, S. and Deffuant, G.}, title = {Modelling and Evaluation of a Risk Management System Case of the BSE Hazard in the Slaughtering Process}, title = {Modélisation et évaluation d'un système de maîtrise des risques. Cas du danger ESB dans le processus d'abattage}, bookTitle = {FOOD'SIM 2000 1st International Conference on Simulation in Food and Bio-industries, Nantes, 26-27 juin 2000}, pages = {277-283}, url = {http://cemadoc.irstea.fr/cemoa/PUB00008303}, year = {2000}, affiliation = {CEMAGREF CLERMONT FERRAND QACF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, number = {00/0249 ; CGR 36}, abstract = {A probabilistic model of risk evaluation in a slaughterhouse is proposed. The aim of the model is to offer the possibility to test different scenarios of preventive measures application. The model is based on: an expert analysis of processes and materials flow in various slaughterhouses a quantification of the BSE risk in terms of infectious doses possibly contained by the materials an evaluation of the probability that a set of preventive measures having an effect on the materials flow is applied. The outputs of the model are numbers of doses at the end of the different pathways of the process and the corresponding probabilities, if an infected animal is slaughtered. / Un modèle probabiliste de l'évaluation du risque dans un abattoir est proposé. L'objectif de la modélisation est de permettre de tester différents scénarios d'application des mesures de maîtrise du risque. Le modèle est fondé sur : l'analyse par des experts du procédé d'abattage et des flux de matières dans différents abattoirs, une quantification du risque ESB en termes de doses infectieuses potentiellement contenues dans les matières, une évaluation de la probabilité qu'un ensemble de mesures de maîtrise, ayant un effet sur les flux de matières, soit effectivement appliqué. Le procédé est ainsi représenté par un graphe. Les sorties du modèle sont les nombres de doses correspondant, dans les cas ou un animal infecté serait abattu, aux différents chemins du graphe et les probabilités correspondantes.}, }
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N. Ferrand, G. Deffuant
Trois apports potentiels des approches " multi-agents " pour l'aide à la décision publique
Colloque Gestion des territoires ruraux - connaissances et méthodes pour la décision publique, Clermont-Ferrand, 27-28 avril 1998 (p. 373-385), Cemagref Editions, Antony, 1998
abs web bib

In this paper, we show which are the potential inputs and drawbacks due to the use of multi-agent approach for analysing, facilitating, and solving public decision problems regarding land use planning and territory management. We propose a methodology, and give three directions, with practical applications : modelling and simulation of multi-actor decision systems, applied to the prospective of new agri-environmental schemes (FAIR-IMAGES project) problem solving for multi-actor multicriteria decision support, applied to path finding for linear infrastructures (SMAALA project) collaborative spatial modelling and decision support, applied to negotiation for spatial project (SANPA project). We propose a generalisation to various classes of public decisions, and we give some perspectives for technical support. By this way, we argue that multi-agent approaches are not limited to computing devices, and imply an integrated problem analysis, pursuing in a practical way the former "systemic" methods. / Dans cette contribution, nous proposons de montrer quels peuvent être les apports potentiels et les difficultés induites par le recours à des approches dites " multi-agents " pour l'analyse, la facilitation et la résolution des situations de décision publique en aménagement et gestion des territoires. Nous proposons une définition méthodologique, et élaborons notre argument selon trois directions, appuyées sur des exemples concrets : modélisation et simulation de systèmes de décision multi-acteurs, appliquée à la prospective des cadres de mesures agri-environnementales (projet IMAGES), résolution de problèmes pour l'aide à la décision multicritères multi-acteurs, appliquée à l'aide à la localisation d'infrastructures linéaires (projet SMAALA), aide à la modélisation et la décision spatiale collaborative, appliquée à la concertation pour les projets d'aménagement (projet SANPA). Nous proposons une extension générale à différentes classes de situations de décisions publiques, et indiquons les perspectives d'assistance technique. Nous cherchons ainsi à illustrer que les approches multi-agents ne se limitent pas à des techniques informatiques, et impliquent une démarche intégrée d'appréhension des problèmes, prolongement pratique des méthodes dites " systémiques ", et toujours fondée sur un principe de description en " base individu / interactions / dynamique ", et sur la possibilité de mettre en oeuvre une image informatique manipulable du système ainsi décrit.
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@inproceedings{PUB00004458, author = {Ferrand, N. and Deffuant, G.}, title = {Trois apports potentiels des approches " multi-agents " pour l'aide à la décision publique}, title = {Multi-agent approach for public decision support}, bookTitle = {Colloque Gestion des territoires ruraux - connaissances et méthodes pour la décision publique, Clermont-Ferrand, 27-28 avril 1998}, address = {Antony}, publisher = {Cemagref Editions}, pages = {373-385}, url = {http://cemadoc.irstea.fr/cemoa/PUB00004458}, year = {1998}, affiliation = {CEMAGREF CLERMONT FERRAND LICF}, number = {98/0112}, abstract = {In this paper, we show which are the potential inputs and drawbacks due to the use of multi-agent approach for analysing, facilitating, and solving public decision problems regarding land use planning and territory management. We propose a methodology, and give three directions, with practical applications : modelling and simulation of multi-actor decision systems, applied to the prospective of new agri-environmental schemes (FAIR-IMAGES project) problem solving for multi-actor multicriteria decision support, applied to path finding for linear infrastructures (SMAALA project) collaborative spatial modelling and decision support, applied to negotiation for spatial project (SANPA project). We propose a generalisation to various classes of public decisions, and we give some perspectives for technical support. By this way, we argue that multi-agent approaches are not limited to computing devices, and imply an integrated problem analysis, pursuing in a practical way the former "systemic" methods. / Dans cette contribution, nous proposons de montrer quels peuvent être les apports potentiels et les difficultés induites par le recours à des approches dites " multi-agents " pour l'analyse, la facilitation et la résolution des situations de décision publique en aménagement et gestion des territoires. Nous proposons une définition méthodologique, et élaborons notre argument selon trois directions, appuyées sur des exemples concrets : modélisation et simulation de systèmes de décision multi-acteurs, appliquée à la prospective des cadres de mesures agri-environnementales (projet IMAGES), résolution de problèmes pour l'aide à la décision multicritères multi-acteurs, appliquée à l'aide à la localisation d'infrastructures linéaires (projet SMAALA), aide à la modélisation et la décision spatiale collaborative, appliquée à la concertation pour les projets d'aménagement (projet SANPA). Nous proposons une extension générale à différentes classes de situations de décisions publiques, et indiquons les perspectives d'assistance technique. Nous cherchons ainsi à illustrer que les approches multi-agents ne se limitent pas à des techniques informatiques, et impliquent une démarche intégrée d'appréhension des problèmes, prolongement pratique des méthodes dites " systémiques ", et toujours fondée sur un principe de description en " base individu / interactions / dynamique ", et sur la possibilité de mettre en oeuvre une image informatique manipulable du système ainsi décrit.}, }
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G. Deffuant
Aller et retour de l'identité logique à l'identité empathique : esquisse d'un cheminement possible
Journées de Rochebrune, 2-9 février 1997 / Invariance, interaction, référence : l'identité en question (p. 69-75), 1997
abs web bib

This text is an extensive summary whose most points would need fuller developments. The general trend of argument is: beginning with the identity in the mathematical sense, we first examine its extension to the identity by stability of shapes, proposed by the morphodynamical theory. We question the applicability of this extension with regards to human social identity. We propose some new directions about this last point, being based on some strong hypotheses about the cognitive functioning. These hypotheses also give us a new perspective on the emergence of the mathematical identity from the mechanisms of the social identity. / Ce texte est un résumé étendu la plupart des points nécessiteraient de plus amples développements. Le mouvement général de l'argumentation est le suivant : partant de l'identité au sens mathématique, nous examinons tout d'abord son extension à l'identité par stabilité des formes prpoposée par la morphodynamique. Nous nous interrogeons sur l'applicabilité de cette extension concernant l'identité sociale des personnes. Nous proposons quelques directions nouvelles sur ce dernier point, en nous fondant sur des hypothèses fortes à propos du fonctionnement cognitif. Ces hypothèses nous donnent également une nouvelle perspective sur l'émergence de l'identité mathématique à partir des mécanismes de l'identité sociale.
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@inproceedings{PUB00013159, author = {Deffuant, G.}, title = {Aller et retour de l'identité logique à l'identité empathique : esquisse d'un cheminement possible}, title = {Return trip from the logical identity to the empathic identity}, bookTitle = {Journées de Rochebrune, 2-9 février 1997 / Invariance, interaction, référence : l'identité en question}, pages = {69-75}, url = {http://cemadoc.irstea.fr/cemoa/PUB00013159}, year = {1997}, affiliation = {CEMAGREF CLERMONT FERRAND LICF}, number = {97/1061}, abstract = {This text is an extensive summary whose most points would need fuller developments. The general trend of argument is: beginning with the identity in the mathematical sense, we first examine its extension to the identity by stability of shapes, proposed by the morphodynamical theory. We question the applicability of this extension with regards to human social identity. We propose some new directions about this last point, being based on some strong hypotheses about the cognitive functioning. These hypotheses also give us a new perspective on the emergence of the mathematical identity from the mechanisms of the social identity. / Ce texte est un résumé étendu la plupart des points nécessiteraient de plus amples développements. Le mouvement général de l'argumentation est le suivant : partant de l'identité au sens mathématique, nous examinons tout d'abord son extension à l'identité par stabilité des formes prpoposée par la morphodynamique. Nous nous interrogeons sur l'applicabilité de cette extension concernant l'identité sociale des personnes. Nous proposons quelques directions nouvelles sur ce dernier point, en nous fondant sur des hypothèses fortes à propos du fonctionnement cognitif. Ces hypothèses nous donnent également une nouvelle perspective sur l'émergence de l'identité mathématique à partir des mécanismes de l'identité sociale.}, }
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Miscellaneous (6)

G. Deffuant
Opinion dynamics in FuturICT
FuturICT meeting, 16/06/2011, Zurich, CHE , 2011
web bib

@misc{PUB00032951, note = {Conférence invitée}, author = {Deffuant, G.}, title = {Opinion dynamics in FuturICT}, title = {Les dynamiques d'opinions dans FuturICT}, bookTitle = {FuturICT meeting, 16/06/2011, Zurich, CHE}, url = {http://cemadoc.irstea.fr/cemoa/PUB00032951}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {}, }
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G. Deffuant, S. Huet, T. Carletti
Leviathan model: vanity generating general distrust or absolute dominance
INTERACTIONS 2011 - Mathematical Sciences to the proof of Human & Social Sciences, 30/05/2011-31/05/2011, Paris, FRA (p. 21), 2011
abs web bib

We propose a simple model made of a population of agents where each one has an opinion about each of the others. The agents interact by randomly chosen pairs and include two different dynamics. One represents gossips where agents propagate their opinions about themselves and some other agents. In this propagation, they influence more the agents that have a good opinion of them. The second dynamics is a vanity effect: an agent likes to get a good opinion of herself from the others, thus she increases her opinion on those who propagate such a good opinion. On the contrary she tends to decrease her opinion about those who propagate a bad opinion (good and bad are relative to the opinion the agent has on herself). The combination of these dynamics shows interesting emergent properties. First, a general distrust tends to prevail for most of the model parameter values: each agent tends to have a negative average opinion about the others. For some parameters, this situation of general distrust leads to the emergence of one or a few agents who are highly considered by all the others, sometimes followed by a hierarchy of reputations with intermediate values. For some parameters, this situation systematically unstable and always ends suddenly with the return to a generalised distrust. We some partial explanations of the mechanisms behind these emergent behaviours.
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@misc{PUB00034526, note = {Conférence invitée}, author = {Deffuant, G. and Huet, S. and Carletti, T.}, title = {Leviathan model: vanity generating general distrust or absolute dominance}, title = {Le modèle Léviathan : la vanité peut engendrer la défiance généralisée ou la domination absolue}, bookTitle = {INTERACTIONS 2011 - Mathematical Sciences to the proof of Human & Social Sciences, 30/05/2011-31/05/2011, Paris, FRA}, pages = {21}, url = {http://cemadoc.irstea.fr/cemoa/PUB00034526}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; UNIVERSITE DE NAMUR BEL}, abstract = {We propose a simple model made of a population of agents where each one has an opinion about each of the others. The agents interact by randomly chosen pairs and include two different dynamics. One represents gossips where agents propagate their opinions about themselves and some other agents. In this propagation, they influence more the agents that have a good opinion of them. The second dynamics is a vanity effect: an agent likes to get a good opinion of herself from the others, thus she increases her opinion on those who propagate such a good opinion. On the contrary she tends to decrease her opinion about those who propagate a bad opinion (good and bad are relative to the opinion the agent has on herself). The combination of these dynamics shows interesting emergent properties. First, a general distrust tends to prevail for most of the model parameter values: each agent tends to have a negative average opinion about the others. For some parameters, this situation of general distrust leads to the emergence of one or a few agents who are highly considered by all the others, sometimes followed by a hierarchy of reputations with intermediate values. For some parameters, this situation systematically unstable and always ends suddenly with the return to a generalised distrust. We some partial explanations of the mechanisms behind these emergent behaviours.}, }
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M. Lenormand, S. Huet, G. Deffuant
Predicting the presence and the number of jobs in different services in Auvergne municipalities
2010
abs web bib

Nous décrivons dans ce rapport une méthode permettant de prédire la présence de différents services (école, boulangerie...) dans une commune en fonction des caractéristiques de celle-ci. Nous présentons aussi une méthode permettant de prédire le nombre d'emplois dans différentes sortes de services. Les deux méthodes sont testées sur les communes d'Auvergne.
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@misc{PUB00035311, note = {Autres}, author = {Lenormand, M. and Huet, S. and Deffuant, G.}, title = {Predicting the presence and the number of jobs in different services in Auvergne municipalities}, title = {Prédire la présence et le nombre d'emplois dans les services pour les communes d'Auvergne}, pages = {9}, url = {http://cemadoc.irstea.fr/cemoa/PUB00035311}, year = {2010}, affiliation = {IRSTEA CLERMONT FERRAND UR LICF FRA ; IRSTEA CLERMONT FERRAND UR LICF FRA ; IRSTEA CLERMONT FERRAND UR LICF FRA}, abstract = {Nous décrivons dans ce rapport une méthode permettant de prédire la présence de différents services (école, boulangerie...) dans une commune en fonction des caractéristiques de celle-ci. Nous présentons aussi une méthode permettant de prédire le nombre d'emplois dans différentes sortes de services. Les deux méthodes sont testées sur les communes d'Auvergne.}, }
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N. Turpin, B. Hautdidier, G. Deffuant, M. Raley
PRIMA, scaling up of case studies
TRUST/RUFUS Workshop Diversities of rural areas in Europe and beyond, 25/08/2010-26/08/2010, Hannovre, DEU , 2010
abs web bib

Facing structural change, European rural areas still fulfil multiple social, economic and ecological functions. Because of scale interplays and sustainability trade-offs, their future dynamics are yet particularly difficult to ascertain. PRIMA aims to develop methods for scaling down the assessment of policy impacts on multifunctional land-use and economic activities. The project focuses on agriculture, forestry, tourism, and ecosystem services, with special attention to the structural effects of the policies. An analysis of the strategic and planning documents in the case study areas highlights that many measures are targeted to several pillars of sustainable development, even though multifunctionality (MF) concept is often unaddressed. Because of the bottom-up governance of the European cohesion policy, a large variety of priorities and measures has been observed, so we oriented the first stakeholders interviews towards their major objectives and the specific measures they activate from the cohesion policy to reach their own objectives. We developed a working regional economic model that interacts between global changes (GTAP-IMAGE interactions) and multi-agent based tool at local level. It covers activities agriculture, forestry, services and nature. A start has been made with a program for downscaling. We are working on a procedure to generate the basic regional data for the input. We have to start data generation and theoretical and empirical work to improve on the allocation procedures of national developments to regions. Considering backbone scenarios, first modelling at European level started, with the identification of key economic and demographic factors that drive land use patterns at regional and local levels. External drivers and policies have been distinguished. GTAP and IMAGES have been linked to provide a working modelling framework. Last, we progressed towards enhancing the scope of IA methods, with a review of literature and extensive work between all workpackages.
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@misc{PUB00032512, note = {Conférence invitée}, author = {Turpin, N. and Hautdidier, B. and Deffuant, G. and Raley, M.}, title = {PRIMA, scaling up of case studies}, bookTitle = {TRUST/RUFUS Workshop Diversities of rural areas in Europe and beyond, 25/08/2010-26/08/2010, Hannovre, DEU}, url = {http://cemadoc.irstea.fr/cemoa/PUB00032512}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR MECF UMR METAFORT FRA ; CEMAGREF BORDEAUX UR ADBX FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; UNIVERSITY OF NEWCASTLE GBR}, abstract = {Facing structural change, European rural areas still fulfil multiple social, economic and ecological functions. Because of scale interplays and sustainability trade-offs, their future dynamics are yet particularly difficult to ascertain. PRIMA aims to develop methods for scaling down the assessment of policy impacts on multifunctional land-use and economic activities. The project focuses on agriculture, forestry, tourism, and ecosystem services, with special attention to the structural effects of the policies. An analysis of the strategic and planning documents in the case study areas highlights that many measures are targeted to several pillars of sustainable development, even though multifunctionality (MF) concept is often unaddressed. Because of the bottom-up governance of the European cohesion policy, a large variety of priorities and measures has been observed, so we oriented the first stakeholders interviews towards their major objectives and the specific measures they activate from the cohesion policy to reach their own objectives. We developed a working regional economic model that interacts between global changes (GTAP-IMAGE interactions) and multi-agent based tool at local level. It covers activities agriculture, forestry, services and nature. A start has been made with a program for downscaling. We are working on a procedure to generate the basic regional data for the input. We have to start data generation and theoretical and empirical work to improve on the allocation procedures of national developments to regions. Considering backbone scenarios, first modelling at European level started, with the identification of key economic and demographic factors that drive land use patterns at regional and local levels. External drivers and policies have been distinguished. GTAP and IMAGES have been linked to provide a working modelling framework. Last, we progressed towards enhancing the scope of IA methods, with a review of literature and extensive work between all workpackages. }, }
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G. Deffuant
Models of opinion dynamics and social influence: From attraction rejection to empathy
Introductory lectures on Aspects of Complexity, 07/09/2009-07/09/2009, Manchester, GBR (p. 46), 2009
abs web bib

This conference makes a state of the art in opinion dynamics modelling.
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@misc{PUB00031484, note = {Conférence invitée}, author = {Deffuant, G.}, title = {Models of opinion dynamics and social influence: From attraction rejection to empathy }, title = {Modèles de dynamiques d'opinion}, bookTitle = {Introductory lectures on Aspects of Complexity, 07/09/2009-07/09/2009, Manchester, GBR}, pages = {46}, url = {http://cemadoc.irstea.fr/cemoa/PUB00031484}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {This conference makes a state of the art in opinion dynamics modelling.}, }
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G. Deffuant
Managing resilience and viability: from formal concepts to practical application
Meeting of Teresa and ETUDE projects workshop, 27/11/2008, Vienne, AUT (p. 29), 2008
web bib

@misc{PUB00032950, note = {Conférence invitée}, author = {Deffuant, G.}, title = {Managing resilience and viability: from formal concepts to practical application}, title = {Résilience et viabilité : des définitions formelles aux approches pratiques}, bookTitle = {Meeting of Teresa and ETUDE projects workshop, 27/11/2008, Vienne, AUT}, pages = {29}, url = {http://cemadoc.irstea.fr/cemoa/PUB00032950}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA}, abstract = {}, }
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Dissertations (1)

G. Deffuant
Modéliser des systèmes complexes : quelques pistes pour relever le défi
Habilitation à Diriger des Recherches, Ecole doctorale SPI de l'Université Blaise Pascal de Clermont-Ferrand, soutenue le 3 mars 2004, 2004
abs pdf web bib

Des hyperplans séparateurs dans des espaces déployés : les Support Vector Machines Les réseaux géométriques dynamiques Modèles géométriques dynamiques pour la diffusion d'opinions : comparer le modèle individu-centré à son approximation agrégée Projet européen IMAGES : un modèle individu-centré de propagation de l'innovation
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@phdthesis{PUB00014157, author = {Deffuant, G.}, title = {Modéliser des systèmes complexes : quelques pistes pour relever le défi}, publisher = {Habilitation à Diriger des Recherches, Ecole doctorale SPI de l'Université Blaise Pascal de Clermont-Ferrand, soutenue le 3 mars 2004}, pages = {133}, pdf = {http://motive.cemagref.fr/_publication/PUB00014157.pdf}, url = {http://wwwlisc.clermont.cemagref.fr/Labo/MembresEtPagesIntermediaires/pagesperso/membres_actuels/deffuant/HDRDeffuantV3.pdf}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00014157}, year = {2004}, affiliation = {CEMAGREF CLERMONT FERRAND LICF}, number = {LI04 2 ; }, abstract = {Des hyperplans séparateurs dans des espaces déployés : les Support Vector Machines Les réseaux géométriques dynamiques Modèles géométriques dynamiques pour la diffusion d'opinions : comparer le modèle individu-centré à son approximation agrégée Projet européen IMAGES : un modèle individu-centré de propagation de l'innovation }, }
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Technical Reports (7)

G. Deffuant, N. Mabrouk, J.D. Mathias, C. Deygout, F. Campillo, A. Lesne
Livrable 2.1 du projet DISCO : Modèles individus-centrés et simulations Monte-Carlo
2011
abs web bib

Les équipes du projet collaborent à plusieurs modèles individus-centrés dans une démarche commune au projet DISCO: ces modèles individus-centrés sont confrontés à la fois à des modèles de type équations aux dérivées partielles ou équations différentielles ordinaires (démarche de "double modélisation") et à des observations venant de démarches expérimentales spécifiques. Cette démarche permet d'identifier clairement les effets spécifiques de l'introduction d'un modèle à partir d'individus. Les modèles individus-centrés donnent lieu aussi dans certains cas à l'émergence de structures spatiales (dans les deux exemples de modèles 2 D) qui étaient difficilement prédictibles initialement. Nous cherchons ensuite à comprendre les mécanismes donnant lieu à ces structures, notamment en définissant des modèles plus simples. Ce rapport présente ces modèles de manière très condensée, le lecteur intéressé pourra trouver les détails dans les documents cités dans les références.
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@techreport{PUB00034524, author = {Deffuant, G. and Mabrouk, N. and Mathias, J.D. and Deygout, C. and Campillo, F. and Lesne, A.}, title = {Livrable 2.1 du projet DISCO : Modèles individus-centrés et simulations Monte-Carlo}, pages = {6}, url = {http://sites.google.com/site/anrdisco/prepr}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00034524}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; INRIA SOPHIA ANTIPOLIS FRA ; INRIA SOPHIA ANTIPOLIS FRA ; UNIVERSITE PIERRE ET MARIE CURIE LPTMC PARIS FRA}, abstract = {Les équipes du projet collaborent à plusieurs modèles individus-centrés dans une démarche commune au projet DISCO: ces modèles individus-centrés sont confrontés à la fois à des modèles de type équations aux dérivées partielles ou équations différentielles ordinaires (démarche de "double modélisation") et à des observations venant de démarches expérimentales spécifiques. Cette démarche permet d'identifier clairement les effets spécifiques de l'introduction d'un modèle à partir d'individus. Les modèles individus-centrés donnent lieu aussi dans certains cas à l'émergence de structures spatiales (dans les deux exemples de modèles 2 D) qui étaient difficilement prédictibles initialement. Nous cherchons ensuite à comprendre les mécanismes donnant lieu à ces structures, notamment en définissant des modèles plus simples. Ce rapport présente ces modèles de manière très condensée, le lecteur intéressé pourra trouver les détails dans les documents cités dans les références.}, }
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N. Turpin, D. Kopeva, M. Raley, O. Baqueiro, G. Deffuant, G. Woltjer, B. Meyer, M. Njavro, L. Jelinek, B. Haudidier, R. Laplana
Periodic Report D0.3 PRIMA collaborative project, EU 7th Framework Programme, contract no. 212345
2010
abs pdf web bib

Facing structural change, European rural areas still fulfil multiple social, economic and ecological functions. Because of scale interplays and sustainability trade-offs, their future dynamics are yet particularly difficult to ascertain. PRIMA aims to develop methods for scaling down the assessment of policy impacts on multifunctional land-use and economic activities. The project focuses on agriculture, forestry, tourism, and ecosystem services, with special attention to the structural effects of the policies. An analysis of the strategic and planning documents in the case study areas highlights that many measures are targeted to several pillars of sustainable development, even though multifunctionality (MF) concept is often unaddressed. Because of the bottom-up governance of the European cohesion policy, a large variety of priorities and measures has been observed, so we oriented the first stakeholders interviews towards their major objectives and the specific measures they activate from the cohesion policy to reach their own objectives. Two groups of stakeholders were identified: those who can assist in scenario and model development and in model validation (drawn from the institutions which implement policy), and the actors who may be affected by the policy and whose behaviour will be captured in the AB model. Two rounds of interviews have been performed, the first one to gain contextual information about the wider case study information. From cluster analysis and this information, sets of municipalities were selected, then a second round of interviews was conducted to identify relevant policy issues and appropriate policy measures. These interviews provide the main events which have occurred during the last 20 years, policy outcomes, the EU funding streams, proposals for new measures. A conceptual model has been developed from extensive literature review and information collected during the surveys. This model focuses on the population dynamics in rural municipalities and on the decision making behaviours observed in such areas, including indicators requirements to match with IA methods. A general method for generating households from different available data at municipality level has been designed: at this level, only average data are available and the method enables to generate relevant individual data to be included in the models. The model has been adapted to the case studies: at this stage, downscaling occurs to input data for the models. We developed a working regional economic model that interacts between global changes (GTAP-IMAGE interactions) and multi-agent based tool at local level. It covers activities agriculture, forestry, services and nature. A start has been made with a program for downscaling. We are working on a procedure to generate the basic regional data for the input. We have to start data generation and theoretical and empirical work to improve on the allocation procedures of national developments to regions. Considering backbone scenarios, first modelling at European level started, with the identification of key economic and demographic factors that drive land use patterns at regional and local levels. External drivers and policies have been distinguished. GTAP and IMAGES have been linked to provide a working modelling framework. Last, we progressed towards enhancing the scope of IA methods, with a review of literature and extensive work between all workpackages. / Le rapport présente le déroulement et les avancées du projet PRIMA à mi parcours de réalisation. Sont présentés les développements en termes d'analyse des politiques et des scénarios, d'implication des parties prenantes dans les processus de modélisation, de conceptualisation des modèles et d'apports pour les procédures d'évaluation des impacts.
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@techreport{PUB00030749, author = {Turpin, N. and Kopeva, D. and Raley, M. and Baqueiro, O. and Deffuant, G. and Woltjer, G. and Meyer, B. and Njavro, M. and Jelinek, L. and Haudidier, B. and Laplana, R.}, title = {Periodic Report D0.3 PRIMA collaborative project, EU 7th Framework Programme, contract no. 212345}, pages = {69}, pdf = {http://motive.cemagref.fr/_publication/PUB00030749.pdf}, url = {https://prima.irstea.fr}, cemadoc = {http://cemadoc.irstea.fr/cemoa/PUB00030749}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR MECF UMR METAFORT FRA ; CEMAGREF CLERMONT FERRAND UR MECF UMR METAFORT FRA ; CEMAGREF CLERMONT FERRAND UR MECF UMR METAFORT FRA ; INSTITUTE OF AGRICULTURAL DEVELOPMENT IN CENTRAL AND EASTERN DEU ; CEMAGREF CLERMONT FERRAND UR LICF FRA ; CEMAGREF CLERMONT FERRAND UR MECF UMR METAFORT FRA ; UNIVERSITY OF TECHNOLOGY DORTMUND DEU ; UNIVERSITE DE ZAGREB KRO ; INSTITUTE OF AGRICULTURAL ECONOMICS AND INFORMATION CZR ; CEMAGREF BORDEAUX UR ADBX FRA ; CEMAGREF BORDEAUX UR ADBX FRA}, abstract = {Facing structural change, European rural areas still fulfil multiple social, economic and ecological functions. Because of scale interplays and sustainability trade-offs, their future dynamics are yet particularly difficult to ascertain. PRIMA aims to develop methods for scaling down the assessment of policy impacts on multifunctional land-use and economic activities. The project focuses on agriculture, forestry, tourism, and ecosystem services, with special attention to the structural effects of the policies. An analysis of the strategic and planning documents in the case study areas highlights that many measures are targeted to several pillars of sustainable development, even though multifunctionality (MF) concept is often unaddressed. Because of the bottom-up governance of the European cohesion policy, a large variety of priorities and measures has been observed, so we oriented the first stakeholders interviews towards their major objectives and the specific measures they activate from the cohesion policy to reach their own objectives. Two groups of stakeholders were identified: those who can assist in scenario and model development and in model validation (drawn from the institutions which implement policy), and the actors who may be affected by the policy and whose behaviour will be captured in the AB model. Two rounds of interviews have been performed, the first one to gain contextual information about the wider case study information. From cluster analysis and this information, sets of municipalities were selected, then a second round of interviews was conducted to identify relevant policy issues and appropriate policy measures. These interviews provide the main events which have occurred during the last 20 years, policy outcomes, the EU funding streams, proposals for new measures. A conceptual model has been developed from extensive literature review and information collected during the surveys. This model focuses on the population dynamics in rural municipalities and on the decision making behaviours observed in such areas, including indicators requirements to match with IA methods. A general method for generating households from different available data at municipality level has been designed: at this level, only average data are available and the method enables to generate relevant individual data to be included in the models. The model has been adapted to the case studies: at this stage, downscaling occurs to input data for the models. We developed a working regional economic model that interacts between global changes (GTAP-IMAGE interactions) and multi-agent based tool at local level. It covers activities agriculture, forestry, services and nature. A start has been made with a program for downscaling. We are working on a procedure to generate the basic regional data for the input. We have to start data generation and theoretical and empirical work to improve on the allocation procedures of national developments to regions. Considering backbone scenarios, first modelling at European level started, with the identification of key economic and demographic factors that drive land use patterns at regional and local levels. External drivers and policies have been distinguished. GTAP and IMAGES have been linked to provide a working modelling framework. Last, we progressed towards enhancing the scope of IA methods, with a review of literature and extensive work between all workpackages. / Le rapport présente le déroulement et les avancées du projet PRIMA à mi parcours de réalisation. Sont présentés les développements en termes d'analyse des politiques et des scénarios, d'implication des parties prenantes dans les processus de modélisation, de conceptualisation des modèles et d'apports pour les procédures d'évaluation des impacts. }, }
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G. Deffuant
An analytical solution to support vector training: the recursive projection algorithm
2003
abs web bib

We propose an algorithm which provides an analytical solution to the problem of norm 2 margin support vector machines (svm) computation. We consider a geometric interpretation of the problem : the svm is defined as the point of a convex polyhedron which is the closest to a particular right line. Our algorithm performs iterative tests of facets of the polyhedron. Each test computes the point of the subspace defining the facet which is the closest to the right line. We show that the svm is such a point satisfying simple conditions. The non satisfaction of these conditions gives indications on the next facet to test. We prove the convergence of the algorithm, and of its use in a variant of the chunking strategy, in general. Our preliminary empirical study of the method suggests that the number of facet tests necessary to find the svm is linear with the number of support vectors. Therefore, the method is particularly interesting when the number of support vectors is low. / Nous proposons un algorithme qui apporte une solution analytique au problème du calcul de support vector machines (svm) dans le cas de l'utilisation de la norme 2 pour traiter les exemples mal classés. Nous considérons une interprétation géométrique du problème. Le svm est défini comme le point d'un polyèdre convexe qui est le plus proche d'une droite particulière de l'espace. Notre algorithme exécute des tests itératifs des facettes du polyèdre. Chaque test calcule le point du sous-espace définissant la facette qui est la plus proche de la droite. Nous montrons que le svm est un tel point satisfaisant des conditions particulières.La non satisfaction de ces conditions donne des indications sur la prochaine facette à tester. Nous prouvons la convergence de l'algorithme et de son utilisation dans une variante de la stratégie chunking, en général.Notre étude empirique préliminaire des méthodes suggère que le nombre de facettes nécessaires pour trouver le svm est linéaire avec le nombre de support vectors.Par conséquent, la méthode est particulièrement intéressante quand le nombre de support vectors est faible.
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@techreport{PUB00011519, author = {Deffuant, G.}, title = {An analytical solution to support vector training: the recursive projection algorithm}, title = {Une solution analytique au problème de l'apprentissage des support vector machines : l'algorithme projection récursive.}, pages = {18}, url = {http://cemadoc.irstea.fr/cemoa/PUB00011519}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LICF}, number = {03/0081 ; LI03 1}, abstract = {We propose an algorithm which provides an analytical solution to the problem of norm 2 margin support vector machines (svm) computation. We consider a geometric interpretation of the problem : the svm is defined as the point of a convex polyhedron which is the closest to a particular right line. Our algorithm performs iterative tests of facets of the polyhedron. Each test computes the point of the subspace defining the facet which is the closest to the right line. We show that the svm is such a point satisfying simple conditions. The non satisfaction of these conditions gives indications on the next facet to test. We prove the convergence of the algorithm, and of its use in a variant of the chunking strategy, in general. Our preliminary empirical study of the method suggests that the number of facet tests necessary to find the svm is linear with the number of support vectors. Therefore, the method is particularly interesting when the number of support vectors is low. / Nous proposons un algorithme qui apporte une solution analytique au problème du calcul de support vector machines (svm) dans le cas de l'utilisation de la norme 2 pour traiter les exemples mal classés. Nous considérons une interprétation géométrique du problème. Le svm est défini comme le point d'un polyèdre convexe qui est le plus proche d'une droite particulière de l'espace. Notre algorithme exécute des tests itératifs des facettes du polyèdre. Chaque test calcule le point du sous-espace définissant la facette qui est la plus proche de la droite. Nous montrons que le svm est un tel point satisfaisant des conditions particulières.La non satisfaction de ces conditions donne des indications sur la prochaine facette à tester. Nous prouvons la convergence de l'algorithme et de son utilisation dans une variante de la stratégie chunking, en général.Notre étude empirique préliminaire des méthodes suggère que le nombre de facettes nécessaires pour trouver le svm est linéaire avec le nombre de support vectors.Par conséquent, la méthode est particulièrement intéressante quand le nombre de support vectors est faible.}, }
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L. Rousseau, S. Bernard, G. Deffuant
Confronting evaluations of scenarios via Internet
2003
abs web bib

We propose a generic software tool supporting participatory decision processes based on simulation of scenarios. The main objective of the tool is to provide information about the state of the participatory process, by enhancing the current consensus and conflicts. The tool provides a generic interface, which is connected to a database of model results. The user can visualise the results corresponding to the scenarios for different attributes of objects located in the space, and a variety of indicators related to these variables. The user expresses evaluations of scenarios by specifying thresholds of acceptance of objects attribute values. The software provides then indicators of comparisons between the expressed evaluations, highlighting the differences of similarities between the expressed evaluation. A series of tests with a group of potential users is currently in progress.
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@techreport{PUB00011350, author = {Rousseau, L. and Bernard, S. and Deffuant, G.}, title = {Confronting evaluations of scenarios via Internet}, title = {Confronter des évaluations sur Internet}, pages = {16}, url = {http://cemadoc.irstea.fr/cemoa/PUB00011350}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, number = {03/0018 ; LI03 2}, abstract = {We propose a generic software tool supporting participatory decision processes based on simulation of scenarios. The main objective of the tool is to provide information about the state of the participatory process, by enhancing the current consensus and conflicts. The tool provides a generic interface, which is connected to a database of model results. The user can visualise the results corresponding to the scenarios for different attributes of objects located in the space, and a variety of indicators related to these variables. The user expresses evaluations of scenarios by specifying thresholds of acceptance of objects attribute values. The software provides then indicators of comparisons between the expressed evaluations, highlighting the differences of similarities between the expressed evaluation. A series of tests with a group of potential users is currently in progress.}, }
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P. Eynard, M. Mas, A. Penciolelli, C. Tinet, G. Deffuant
Développement d'un outil pour la modélisation du risque ESST dans les filières viandes et co-produits, pour l'aide à la décision en matière de réglementation et de prévention : rapport de recherche
2001
abs web bib

To reduce the risk of transfer of bovine spongiform encephalopathy infectivity to man and cattle, specified risk material have been excluded from entering the food chain. A stochastic model has been developed to compute a risk level taking into account the technical features of the process as well as the characteristics of the risk management system. The model computes flows of products - especially those of tissues which potentially carry BSE infectivity. Software including a man-machine interface for the designing of models and a tree computation algorithm allows a number of applications such as comparing scenarios or ranking the preventive measures according to their efficiency in risk reduction. These applications are illustrated using to particular models : i) the slaughtering process, ii) the collection, rendering and eventually destruction of wastes. Then the possibility of combining these two models in order to characterise the risk along the all slaughtering and waste processing chain is demonstrated. / Pour réduire le risque de transmission de l'encéphalopathie spongiforme bovine à l'homme et à l'animal, les matières à risques sont retirées de la chaîne alimentaire. Un modèle stochastique a été développé afin d'apprécier ce risque en tenant compte des défaillances possibles du système de retrait ainsi que des caractéristiques techniques du procédé. Ce modèle calcule les flux de matières -et donc en particulier des tissus potentiellement vecteurs de l'agent de l'ESB- au cours des procédés de transformation de la filière viande et des filières des co-produits. Une maquette logicielle, composée d'une interface de création du modèle de filière associée à un algorithme de parcours d'arbre, permet plusieurs applications de la méthode : comparaison de scénarios, hiérarchisation des mesures de maîtrise du risque. Elles sont illustrées dans le rapport grâce à deux modèles : celui du procédé d'abattage et celui de la collecte et de la transformation des déchets. On montre ensuite comment les résultats obtenus sur ces deux modèles partiels peuvent être combinés pour aboutir à une caractérisation globale du risque.
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@techreport{PUB00010058, author = {Eynard, P. and Mas, M. and Penciolelli, A. and Tinet, C. and Deffuant, G.}, title = {Développement d'un outil pour la modélisation du risque ESST dans les filières viandes et co-produits, pour l'aide à la décision en matière de réglementation et de prévention : rapport de recherche}, title = {Modeling the risk related to ESST in the meat and by-products production chains : a tool for decision making: research report}, pages = {27}, url = {http://cemadoc.irstea.fr/cemoa/PUB00010058}, year = {2001}, affiliation = {CEMAGREF CLERMONT FERRAND UR TSCF FRA ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, number = {01/0787 ; TS01 13}, abstract = {To reduce the risk of transfer of bovine spongiform encephalopathy infectivity to man and cattle, specified risk material have been excluded from entering the food chain. A stochastic model has been developed to compute a risk level taking into account the technical features of the process as well as the characteristics of the risk management system. The model computes flows of products - especially those of tissues which potentially carry BSE infectivity. Software including a man-machine interface for the designing of models and a tree computation algorithm allows a number of applications such as comparing scenarios or ranking the preventive measures according to their efficiency in risk reduction. These applications are illustrated using to particular models : i) the slaughtering process, ii) the collection, rendering and eventually destruction of wastes. Then the possibility of combining these two models in order to characterise the risk along the all slaughtering and waste processing chain is demonstrated. / Pour réduire le risque de transmission de l'encéphalopathie spongiforme bovine à l'homme et à l'animal, les matières à risques sont retirées de la chaîne alimentaire. Un modèle stochastique a été développé afin d'apprécier ce risque en tenant compte des défaillances possibles du système de retrait ainsi que des caractéristiques techniques du procédé. Ce modèle calcule les flux de matières -et donc en particulier des tissus potentiellement vecteurs de l'agent de l'ESB- au cours des procédés de transformation de la filière viande et des filières des co-produits. Une maquette logicielle, composée d'une interface de création du modèle de filière associée à un algorithme de parcours d'arbre, permet plusieurs applications de la méthode : comparaison de scénarios, hiérarchisation des mesures de maîtrise du risque. Elles sont illustrées dans le rapport grâce à deux modèles : celui du procédé d'abattage et celui de la collecte et de la transformation des déchets. On montre ensuite comment les résultats obtenus sur ces deux modèles partiels peuvent être combinés pour aboutir à une caractérisation globale du risque.}, }
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S. Huet, G. Deffuant
Calcul de l'impact économique de la conversion à l'agriculture biologique : projet IMAGES, modèle Allier Conversion à l'agriculture biologique
2001
abs web bib

The objective was to simulate the calculation that farmers from Allier department can make when they have to take a decision about using or not an environmental measure. Farms diversity has been taken into account. The calculation was based on three steps: identification of available data and possible variation of Images model parameters - modelling of the calculation - selection of parameters to be used for impact calculation by Images model. / Ce travail a pour objectif de définir un calcul d'impact économique de la conversion à l'agriculture biologique pour les exploitations agricoles du département de l'Allier. Il s'inscrit dans le cadre du modèle élaboré dans le projet IMAGES, qui simule les processus de décision des agriculteurs confrontés au choix d'adopter ou non une mesure agri-environnementale. L'objectif est donc ici de simuler le calcul que peuvent faire les agriculteurs au moment de la décision, c'est-à-dire en tenant compte de nombreuses incertitudes. Le modèle IMAGES a pour objectifs de simuler les décisions de l'ensemble de la population des agriculteurs de l'Allier, en prenant au maximum en compte la diversité des exploitations. Le calcul d'impact économique de la conversion doit donc être applicable avec le maximum de réalisme à l'ensemble de cette diversité. Ce type de calcul n'existe pas dans la littérature. En effet, il n'existe pour le moment aucune référence solide, applicable dans tous les cas de figure et admise par tous, qui permette de mesurer les rendements en agriculture biologique. Ainsi, pour réaliser un tel calcul, trois grandes étapes sont nécessaires : - identification des données disponibles et des plages de variations possibles des paramètres du modèle - modélisation du calcul réalisé par le technicien de la Chambre d'Agriculture de l'Allier - exploration des paramètres du modèle et sélection de jeux de paramètres à utiliser pour le calcul d'impact du modèle Images par élimination des résultats paraissant aberrants. L'innovation principale de ce travail est de proposer des évaluations du potentiel de l'agriculture biologique en Auvergne et dans l'Allier en terme d'exploitations économiquement intéressées à se convertir (nombre d'exploitations, caractéristiques, ...).
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@techreport{PUB00009543, author = {Huet, S. and Deffuant, G.}, title = {Calcul de l'impact économique de la conversion à l'agriculture biologique : projet IMAGES, modèle Allier Conversion à l'agriculture biologique}, title = {Effect calculation of conversion to biologic agriculture on economy: IMAGES project, Allier Department model Conversion to biologic agriculture}, pages = {77}, url = {http://cemadoc.irstea.fr/cemoa/PUB00009543}, year = {2001}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF}, number = {01/0399 ; IAS 78}, abstract = {The objective was to simulate the calculation that farmers from Allier department can make when they have to take a decision about using or not an environmental measure. Farms diversity has been taken into account. The calculation was based on three steps: identification of available data and possible variation of Images model parameters - modelling of the calculation - selection of parameters to be used for impact calculation by Images model. / Ce travail a pour objectif de définir un calcul d'impact économique de la conversion à l'agriculture biologique pour les exploitations agricoles du département de l'Allier. Il s'inscrit dans le cadre du modèle élaboré dans le projet IMAGES, qui simule les processus de décision des agriculteurs confrontés au choix d'adopter ou non une mesure agri-environnementale. L'objectif est donc ici de simuler le calcul que peuvent faire les agriculteurs au moment de la décision, c'est-à-dire en tenant compte de nombreuses incertitudes. Le modèle IMAGES a pour objectifs de simuler les décisions de l'ensemble de la population des agriculteurs de l'Allier, en prenant au maximum en compte la diversité des exploitations. Le calcul d'impact économique de la conversion doit donc être applicable avec le maximum de réalisme à l'ensemble de cette diversité. Ce type de calcul n'existe pas dans la littérature. En effet, il n'existe pour le moment aucune référence solide, applicable dans tous les cas de figure et admise par tous, qui permette de mesurer les rendements en agriculture biologique. Ainsi, pour réaliser un tel calcul, trois grandes étapes sont nécessaires : - identification des données disponibles et des plages de variations possibles des paramètres du modèle - modélisation du calcul réalisé par le technicien de la Chambre d'Agriculture de l'Allier - exploration des paramètres du modèle et sélection de jeux de paramètres à utiliser pour le calcul d'impact du modèle Images par élimination des résultats paraissant aberrants. L'innovation principale de ce travail est de proposer des évaluations du potentiel de l'agriculture biologique en Auvergne et dans l'Allier en terme d'exploitations économiquement intéressées à se convertir (nombre d'exploitations, caractéristiques, ...).}, }
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G. Deffuant, F. Amblard, S. Huet, S. Bernard, N. Ferrand, J.P. Bousset, G. Amon, J. Henriot
Projet européen IMAGES :Simulation de l'évolution des conversions à l'agriculture biologique dans le département de l'Allier entre 1994 et 1999 par un modèle multi-agents Rapport d'avancement du cas Allier
2000
abs web bib

Nous présentons un modèle permettant de simuler l'évolution des conversions à l'agriculture biologique dans le département de l'Allier entre 1994 et 1999. Le modèle se nourrit d'enquêtes réalisées sur le terrain ainsi que de données statistiques diverses. Il se fonde sur une reconstitution valide statistiquement de la population d'agriculteurs du département et leur localisation par commune. Les réseaux sociaux des agriculteurs (constitué d'autres agriculteurs et d'acteurs institutionnels) sont considérés dans le modèle. La décision de conversion est modélisée comme le résultat d'un processus comprenant plusieurs étapes. Intéractions sociales et calculs économiques se mêlent étroitement dans ce processus. L'objectf du modèle à terme est de fournir des tendances prospectives sur les évolutions futures des conversions, en fonction d'hypothèses sur l'évolution du contexte économique et politique.
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@techreport{PUB00009312, author = {Deffuant, G. and Amblard, F. and Huet, S. and Bernard, S. and Ferrand, N. and Bousset, J.P. and Amon, G. and Henriot, J.}, title = {Projet européen IMAGES :Simulation de l'évolution des conversions à l'agriculture biologique dans le département de l'Allier entre 1994 et 1999 par un modèle multi-agents Rapport d'avancement du cas Allier}, pages = {21}, url = {http://cemadoc.irstea.fr/cemoa/PUB00009312}, year = {2000}, affiliation = {CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND LICF ; CEMAGREF CLERMONT FERRAND DFCF ; CEMAGREF CLERMONT FERRAND DFCF ; CEMAGREF CLERMONT FERRAND DFCF}, number = {00/0843}, abstract = {Nous présentons un modèle permettant de simuler l'évolution des conversions à l'agriculture biologique dans le département de l'Allier entre 1994 et 1999. Le modèle se nourrit d'enquêtes réalisées sur le terrain ainsi que de données statistiques diverses. Il se fonde sur une reconstitution valide statistiquement de la population d'agriculteurs du département et leur localisation par commune. Les réseaux sociaux des agriculteurs (constitué d'autres agriculteurs et d'acteurs institutionnels) sont considérés dans le modèle. La décision de conversion est modélisée comme le résultat d'un processus comprenant plusieurs étapes. Intéractions sociales et calculs économiques se mêlent étroitement dans ce processus. L'objectf du modèle à terme est de fournir des tendances prospectives sur les évolutions futures des conversions, en fonction d'hypothèses sur l'évolution du contexte économique et politique.}, }
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Irstea Motive