like ours can be useful for evidence-based decision-making in urban planning. Several questions remain open, however, and would need further investigation.

#### Scale of the model

One ambiguity of the model is that it can be applied at different scales, therefore there is no unique correspondence between its agents and the real world. As the above results illustrate, the simulated urban configurations may represent a system of cities at the macroscopic scale, the neighborhoods of one city at the mesoscopic scale, or the buildings of one district at the microscopic scale. Without engaging in an ontological debate over levels of abstraction, this could still be pointed out as a potential issue.

We wish to argue, however, that the multiscale applicability of our model is legitimate as a great number of urban systems and associated dynamics have been shown to be “scale-free”, in particular by Pumain [@pumain2004scaling], and even to possess fractal properties, by Batty [@FractalCities]. It means that scaling laws may also operate in our model, therefore qualitative results should remained unchanged while the quantitative evolution of variables and relations should only depend on the underlying power law’s exponent.

Barthélemy [@2013arXiv1309.3961L] warns that most multi-agent urban models fail because they 