Summary: Forward Reachability Analysis of Timed Petri Nets
Parosh Aziz Abdulla, Johann Deneux, Pritha Mahata, and Aletta Nyl’en
Uppsala University, Sweden
fparosh,johannd,pritha,alettag@it.uu.se
Abstract. We consider verification of safety properties for concurrent real­timed
systems modelled as timed Petri nets, by performing symbolic forward reachability
analysis. We introduce a formalism, called region generators for representing sets of
markings of timed Petri nets. Region generators characterize downward closed sets
of regions, and provide exact abstractions of sets of reachable states with respect
to safety properties. We show that the standard operations needed for performing
symbolic reachability analysis are computable for region generators. Since forward
reachability analysis is necessarily incomplete, we introduce an acceleration tech­
nique to make the procedure terminate more often on practical examples. We have
implemented a prototype for analyzing timed Petri nets and used it to verify a pa­
rameterized version of Fischer's protocol and a producer­consumer protocol. We
also used the tool to extract finite­state abstractions of these protocols.
1 Introduction
Timed Petri nets (TPNs) are extensions of Petri nets in the sense that each token has
an ``age'' which is represented by a real valued clock (see [Bow96] for a survey). TPNs
are computationally more powerful than timed automata [AD90], since they operate on

Source: Abdulla, Parosh Aziz - Department of Information Technology, Uppsala Universitet

Collections: Computer Technologies and Information Sciences