REASONING ABOUT SYSTEMS WITH MANY PROCESSES

Methods are given for automatically verifying temporal properties of concurrent systems containing an arbitrary number of finite-state processes that communicate using CCS actions. Two models of systems are considered. Systems in the first model consist of a unique control process and an arbitrary number of user processes with identical definitions. For this model, a decision procedure to check whether all the executions of a process satisfy a given specification is presented. This algorithm runs in time double exponential in the sizes of the control and the user process definitions. It is also proven that it is decidable whether all the fair executions of a process satisfy a given specification. The second model is a special case of the first. In this model, all the processes have identical definitions. For this model, an efficient decision procedure is presented that checks if every execution of a process satisfies a given temporal logic specification. This algorithm runs in time polynomial in the size of the process definition. It is shown how to verify certain global properties such as mutual exclusion and absence of deadlocks. Finally, it is shown how these decision procedures can be used to reason about certain systems with a communication network.