A great number of processes for multi-agent systems design have been presented in last years to support the different approaches to agent-oriented design; each process is specific for a particular class of problems and it instantiates a specific MAS meta-model. These differences produce inconsistences and overlaps: a MAS meta-model may define a term not referred by another, or the same term can be used with a different meaning.
We think that the lack of a standardization may cause a significant delay to the diffusion of the agent paradigm outside research context. Working for this unification goal, it is also necessary to define in unambiguous way the terms of the agent model and their relationships thus obtaining a unified MAS meta-model. In this work we propose the PASSI MAS meta-model, the results of its adaptation to the needs of an agile process (Agile PASSI), and a comparison with an existing unifying proposal of MAS meta-model composed by considering three different processes (ADELFE, Gaia and PASSI).