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Summary: Timed Petri Nets and BQOs
Parosh Aziz Abdulla and Aletta Nylen
Department of Computer Systems, Uppsala University
P.O. Box 337, SE-751 05 Uppsala, Sweden
fparosh, alettag@docs.uu.se
Abstract. We consider (unbounded) Timed Petri Nets (TPNs) where
each token is equipped with a real-valued clock representing the \age"
of the token. Each arc in the net is provided with a subinterval of the
natural numbers, restricting the ages of the tokens travelling the arc.
We apply a methodology developed in [AN00], based on the theory of
better quasi orderings (BQOs), to derive an eÆcient constraint system
for automatic veri cation of safety properties for TPNs. We have imple-
mented a prototype based on our method and applied it for veri cation
of a parametrized version of Fischer's protocol.
1 Introduction
One of the most widely used techniques for automatic veri cation of programs
is that of model checking [CES86,QS82]. A major current challenge is to extend
the applicability of model checking to the context of in nite-state systems. A
program may be in nite-state since it operates on unbounded data structures,
e.g. timed automata [ACD90], hybrid automata [Hen95], data-independent sys-
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