Liveness and Fairness in Process-Algebraic Verification

Abstract

Although liveness and fairness have been used for a long time in classical model checking, with process-algebraic methods they have seen far less use. One reason for this is that most well-known process-algebraic theories such as CSP and CCS have limited capability for handling liveness properties. In this article we discuss the problems and possibilities of liveness and fairness in process algebra. We show that most well-known semantic equivalences do not preserve enough fairness-related information and that fairness properties are difficult to combine with the bottom-up compositionality of process algebra. However, we also establish positive results for a useful subset of fairness properties. We develop a method that does not assume new fairness-related constructs or rules for processes, but uses the standard LTS model. We demonstrate the method by removing livelocks from a communication protocol.