Presented at the “Model to Model” workshop, 31st March/1st April 2003, Marseille.
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 activated by a Brownian movement. We thus have an aggregated numerical model, as well as an individual-based model of this phenomenon. We consider various alternatives of this example, which lead to different use of the virtual laboratory. We consider in particular the coupling between the two models in which the aggregate model asks for calculations of parameters to the individual-based model. We evoke finally the case of scale shifts in the models and the way it can be managed by this type of approach.