Verification of Liveness Properties on Closed Timed-Arc Petri Nets

Verification of closed timed models by explicit state-space exploration methods is an alternative to the wide-spread symbolic techniques based on difference bound matrices (DBMs). A few experiments found in the literature confirm that for the reachability analysis of timed automata explicit techniques can compete with DBM-based algorithms, at least for situations where the constants used in the models are relatively small. To the best of our knowledge, the explicit methods have not yet been employed in the verification of liveness properties in Petri net models extended with time. We present an algorithm for liveness analysis of closed Timed-Arc Petri Nets (TAPN) extended with weights, transport arcs, inhibitor arcs and age invariants and prove its correctness. The algorithm computes optimized maximum constants for each place in the net that bound the size of the reachable state-space. We document the efficiency of the algorithm by experiments comparing its performance with the state-of-the-art model checker UPPAAL.