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A conceptual model for multipoints of view analysis of complex systems. Application to the analysis of the carbon dynamics of village territories of the west African savanna

Belem M.. 2009. Montpellier : AgroParisTech, 189 p.. Thèse de doctorat -- Informatique et simulation.

Modelling complex systems that cover multiple domains, for their better understanding, increasingly demands collaboration between different disciplines. However, these disciplines do not necessarily share the same points of view on the real objects of the system, and these can be complementary. In addition, the representation of such systems requires multi-scale description implying at least the local (individual), global and underlying environment. This PhD work proposes (1) a conceptual framework for complex systems analysis and representation from different points of view at the global and the local levels while taking into account the environment and (2) its application to the representation and analysis of the carbon dynamics from plot to village levels in the West African savannas (WAS). Using multi-agent system (MAS) organizations-centered approach, the Organization-Role- Entity-Aspect (OREA) meta-model has been proposed to represent a complex system from different points of view. At the global level a point of view is reified as an organization made of the roles the entities can play in the organization; at the local level the points of view decompose an entity internal structure in a set of aspects. Through the concept of role, an entity can play different roles in different organizations. Through the concept of aspects, an entity can play a role in different ways. OREA is an extension of the Agent-Group-Role meta-model where: (1) roles are not limited to agents but can be assigned to any kind of object (including the environment), (2) the decomposition does not only apply to the organizations only, but also to the entities themselves, (3) the use of the framework for knowledge representation rather than a pure software engineering paradigm is emphasized. OREA provides a framework to specify explicitly and separately the macro and the micro levels. The macro-level in OREA is specified without any assumption on the micro-level. The macro-level is relevant to the "what" while the micro-level is concerned by the "how". The environmental objects are explicitly defined in the organization structure allowing defining the perception of the environment by the entities through their roles. The OREA methodology allows specification of the structure of a system based on the identification of the scales of description and their underlying processes. The OREA model has then been used for the modelling of the carbon (C) dynamics from plot to village levels in the WAS. Carbon is an important determinant of the sustainability of West African farming systems and of the greenhouse effect. To deal with the complexity of C dynamics various models have been developed to simulate and predict carbon dynamics. These models are mathematical, process-based or individual-based. To better include social and economic dimension and handle system heterogeneity a generic multi-agent model for the analysis of C dynamics at the village level, CaTMAS (Carbon Territory Multi-Agent Simulator), has been designed and implemented. CaTMAS assumes that a better analysis of C dynamics at the village level requires consideration of (1) social, economic, physical and biological factors, (2) the individual's actions and the multiplicity of interleaved dynamics. CaTMAS is based on the OREA model, the MAS approach, and coupling with the Century model and a Geographic Information System. The model allows a multiple-point-of-view analysis of C dynamics as organisations made of roles played by entities through various aspects. CaTMAS not only provides a framework for an explicit and realistic description of a farming system but also allows assessment of the viability of farming systems under various socio-economic and bio-physical scenarios. The model integrates the interactions between the human's activities and the environment and some environmental feedbacks. Using CaTMAS, it is possible to analyze how population growth impacts C dynamics and vice-versa. The mod...

Mots-clés : changement climatique; système de culture; village; cycle du carbone; modèle de simulation; afrique occidentale

Thématique : Méthodes mathématiques et statistiques; Météorologie et climatologie; Chimie et physique du sol

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