Symbolic Unfolding of Parametric Stopwatch Petri Nets
Résumé
This paper proposes a new method to compute symbolic unfoldings for safe Stopwatch Petri Nets (SwPNs), extended with time parameters, that symbolically handle both the time and the parameters. We propose a concurrent semantics for (parametric) SwPNs in terms of timed processes à la Aura and Lilius. We then show how to compute a symbolic unfolding for such nets, as well as, for the subclass of safe time Petri nets, how to compute a finite complete prefix of this unfolding. Our contribution is threefold: unfolding in the presence of stopwatches or parameters has never been addressed before. Also in the case of time Petri nets, the proposed unfolding has no duplication of transitions and does not require read arcs and as such its computation is more local. Finally the unfolding method is implemented (for time Petri nets) in the tool Romeo.