Towards Integrated Verification of Timed Transition Models

Abstract

This paper describes an attempt to combine theorem proving and model-checking to formally verify real-time systems in a discrete time setting. The Timed Automata Modeling Environment (TAME) has been modified to provide a formal model for Time Transition Models (TTMs) in the PVS proof checker. Strong and weak state-event observation equivalences are formalized in PVS for state-event labeled transition systems (SELTS), the underlying semantic model of TTMs. The state-event equivalences form the basis of truth value preserving abstractions for a real-time temporal logic. When appropriate restrictions are placed upon the TTMs, their PVS models can be easily translated into input for the SAL model-checker. A simple real-time control system is specified and verified using these theories. While these preliminary results indicate that the combination of PVS and SAL could provide a useful environment to perform equivalence verification, model-checking and compositional model reduction of real-time systems, the current implementation in the general purpose SAL model-checker lags well behind state of the art real-time model-checkers.