  The integration of multiple viewpoints became an increasingly popular
approach to deal with agent-based simulations. Despite their disparities,
recent approaches successfully manage to run such multi-level simulations. Yet,
are they doing it appropriately?
  This paper tries to answer that question, with an analysis based on a generic
model of the temporal dynamics of multi-level simulations. This generic model
is then used to build an orthogonal approach to multi-level simulation called
SIMILAR. In this approach, most time-related issues are explicitly modeled,
owing to an implementation-oriented approach based on the influence/reaction
principle.
