Specifying Urgency in Timed I/O Automata

B. Gebremichael and F.W. Vaandrager. Specifying Urgency in Timed I/O Automata. In B.K. Aichernig and B. Beckert, editors. Proceedings of the 3rd IEEE International Conference on Software Engineering and Formal Methods (SEFM 2005), Koblenz, Germany, September 5-9, 2005. IEEE Computer Society, pages 64-73.
Full version available as Technical Report NIII-R0459, NIII, Radboud University Nijmegen, December 2004.


Sifakis et al advocate the use of deadline predicates for the specification of progress properties of Alur-Dill style timed automata. In this article, we extend these ideas to a more general setting, which may serve as a basis for deductive verification techniques. More specifically, we extend the TIOA framework of Lynch et al with urgency predicates. We identify a suitable language to describe the resulting timed I/O automata with urgency and show that for this language time reactivity holds by construction. We also establish that the class of timed I/O automata with urgency is closed under composition. The use of urgency predicates is compared with three alternative approaches to specifying progress properties that have been advocated in the literature: invariants, stopping conditions and deadlines predicates. We argue that in practice the use of urgency predicates leads to shorter and more natural specifications than any of the other approaches. Some preliminary results on proving invariant properties of timed (I/O) automata with urgency are presented.

SEFM 2005 proceedings version (pdf)
SEFM 2005 slides (pdf)
NIII report (pdf)