This article introduces a formal model to specify, model and validate hierarchical complex systems described at different levels of analysis. It relies on concepts that have been developed in the multi-agentbased simulation (MABS) literature: level, influence and reaction. One application of such model is the specification of hierarchical complex systems, in which decisional capacities are dynamically adapted at each level with respect to the emergences/constraints paradigm. In the conclusion, we discuss the main perspective of this work: the definition of a generic meta-model for holonic multi-agent systems (HMAS).Keywords: multi-level multi-agent based simulations, formal models, hierarchical systems 2 The presentation focuses on the influences → reaction model (IRM). Other approaches such as IODA [10] or based on DEVS [18] are not described. 3 Multi-level approaches have proven useful in many domain such as statistics [8], chemistry [9,11], physics [28], hydrology [26] or biology [33].