Finite - State Concurrent Systems ?

Temporal logic model checking is an automatic technique for verifying nite-state concurrent systems. Speciications are expressed in a propositional temporal logic, and the concurrent system is modeled as a state-transition graph. An eecient search procedure is used to determine whether or not the state-transition graph sat-isses the speciication. When the technique was rst developed ten years ago, it was only possible to handle concurrent systems with a few thousand states. In the last few years, however, the size of the concurrent systems that can be handled has increased dramatically. By representing transition relations and sets of states implicitly using binary decision diagrams, it is now possible to check concurrent systems with more than 10 120 states. In this paper we describe in detail how the new implementation works and give realistic examples to illustrate its power. We also discuss a number of directions for future research. The necessary background information on binary decision diagrams, temporal logic, and model checking has been included in order to make the exposition as self-contained as possible.