“…Four main theoretical issues emerge in the literature on multi-level 1 agent-based modeling: the conception of a meta-model allowing a non ambiguous characterization of a multi-level model at the conceptual level [18,23,29,33], the introduction of a dynamic level of detail [25,31], the detection and reification of emergent phenomena [2,3,5,21,30,34] and the representation of aggregated entities [27]. This paper focuses on the first one, with respect to the Influence Reaction (IR) principle, shortly, action as a two step process: (1) agents produce "influences", i.e., individual decisions, according to their internal state and perceptions (2) the system "reacts", i.e., computes the consequences of influences, according to the state of the world [10].…”