Clarifying the priority specification of GSPN: Detached priorities

The global multilevel priority definition in GSPN, while being most convenient with many respects, poses some modelling problems related with confusion and indirect conflicts, which may lead to undesired effects in the definition of the underlying stochastic process. While some of these problems have been recognized and dealt with in previous works on the definition of GSPN, through the introduction of extended conflict sets, some others, that will be illustrated in this paper, were not covered. To overcome all these problems, in this paper a syntactical subclass of GSPN, called detached priorities GSPN (dpGSPN), is proposed. In dpGSPN no confusion or indirect conflicts are possible, and according to our experience, modelling power is not substantially sacrificed. To facilitate the modelling, a possible method to derive a suitable global priority definition from local information is outlined