For concurrent and large systems, specification step is a crucial point. Combinatory explosion is a limit that can be encountered when a state space exploration is driven on large specification modeled with Petri nets. Considering bounded Petri nets, technics like unfolding can be a way to cope with this problem. This paper is a first attempt to present an axiomatic model to produce the set of processes of unfoldings into a canonic form. This canonic form allows to define a conflict equivalence.