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some recompositions at the level of the cities and their interactions. At that level the
responses to change are much more diversified.
The analogy mentioned by Stanilov and Batty [STA 10], between the
fundamental rules governing the evolution of a city's land use and a “genetic code”,
would also be fully meaningful for the EuroSim model. During a period as long as a
century, the economic and technological contexts are profoundly modified (new
economic functions emerge, the travelling times change, etc.), but the driving force
of the system of cities' dynamics is the same: each city seeks to enhance its relative
position in the urban system through the interactions with the other cities belonging
to its different networks of exchanges. As a matter of fact, it is the success of these
interactions (in terms of trade) which secures its place in the urban hierarchy, or
even makes it move up in this hierarchy.
4.4. Conclusion
The methods presented in this fourth chapter have in common the fact that they
are intrinsically dynamic and are mobilized in the context of an explanatory
approach in social sciences. The aim is to formalize the process that leads to change,
the focus being on: segregation (Schelling's model, Yaffo's model and school
inequality model), growth, concentration and hierarchization (models of the Pueblo
of Mesa Verde and Eurosim), abandonment (models of the Maya, the Anazasis and
the Pueblos) and diffusion (land occupation and periurbanisation). The modeling
formalisms are varied and the preference for one rather than the other depends on
the scientific habits, the objectives and the hypotheses of the mechanisms involved
in the processes at stake. The objects, attributes and relations are then identified in a
manner consistently relative to the problematics and the chosen method:
- the CA approach will be adapted if the hypotheses can be formalized in terms
of cells that change state depending on the state of neighboring cells;
-the microsimulation: if the consistency of family construction and
demographic aspects play a key role in the evolution of the system;
- an MAS: if a direct or indirect interaction with other agents affects the
behavior of an agent.
Indeed, interactions and driving forces of change are of a different nature
depending on the type of models. The applications show a clear difference between
microsimulation on the one hand and MAS and CA on the other hand. In the
applications of microsimulation in social sciences, the interactions mainly refer to
the dependence of the decision of some, to that of the others:
