GSPNs versus SPNs: what is the actual role of immediate transitions?

Stochastic Petri nets (SPNs) and generalized stochastic Petri nets (GSPNs) are compared in order to investigate the role of immediate transitions. The comparison is based on the ability of the two formalisms to define models that can be `scalable´ with respect to the initial marking. An intermediate model between (G)SPN structures and (G)SPN systems called `family´ is introduced as a reference for the comparison. It is shown that GSPN families exist that do not have SPN counter- parts. An algorithm is given to reduce GSPN to SPN families in the cases in which this is possible. The application of this structural reduction algorithm allows a more efficient generation of the state space of GSPN systems