Verification of Dense Time Properties Using Theories of Untimed Process Algebra

Abstract

The article shows how untimed process algebraic methods can be used in verifying a category of dense time properties from a restricted class of timed automata. The work is based on the known results that if we restrict ourselves to a certain class of timed automata, then most of the interesting dense time properties are verifiable using discrete time methods. Those results are refined here in order to fit the process algebraic context, and furthermore, reduction strategies based on behavior equivalences, compositionality and abstraction are indicated. The usability of the method is evaluated with two case studies.ity Keywords: Formal verification, Timed automata, Process algebra, Compositional- I N T R O D U C T I O NBecause of the state explosion problem, a useful principle in algorithmic verification is that the information unnecessary for a verification task should be abstracted away. Especially, we would like to see in the context of systems specified with timed automata when it is sufficient to use discrete time algorithms but still say something about the system behavior in dense time.In Henzinger et al., 1992 it was shown that for systems specified with timed transition systems, a large class of dense time properties can be verified by using discrete time algorithms. These results were generalized to timed automata in Bošna ki, 1999. In this article we show how the methods used in standard untimed process algebra, and the related tools, can be used in verifying this category of dense time properties