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 savannas
Computer Simulation, Multi-Agents System, Multi-point of view, Organisation, OREA, Renewable resources, carbon resources, CaTMAS
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 been tested and validated through the analysis, the design and the implementation of a simulation tool : the Carbon Territory Multi-Agents Simulation (CaTMAS) model. 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. The model has been used to analyze the impacts of climate and economic change on the one hand, and of two cropping systems on the other hand, on the C dynamics of the village territory.
Future efforts on the OREA model should focus on improving the methodology and the verification and on taking into account the holonic representation. Developments on CaTMAS could include enlargement of simulations to the country scale and integration of the economic potential of the C market at the national, regional and the local levels.
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Thèse soutenue le 16 septembre 2009 devant le jury suivant :
Post-doc à l'Institut International d'ingénierie de l'eau et de l'environnement, Ouagadougou, Burkina-Faso.