The MAS engineering is becoming very important, it is concerned with models, methods and tools. Therefore, verifying the correctness of MAS is the next challenge. We are interested by MAS where each participating agent has its own physical clock of varying frequency, while no global clock is available or desirable. Under such circumstances models must be adapted. In this paper we attempt a novel approach to model the MAS, with a respect of two characteristics, the concurrent aspect and heterogeneity of agents (perceived as a different time rates of agents plan execution). Timed automata with action durations are used; for the circumstance it’s extended to deal with relative time rates. Its semantic is abstracted by a novel equivalence relation leading to a region automaton for decidability assessment and proof.