Constraint Orientated Specification with CSP and Real Time Temporal Logic

Abstract

this paper we propose such a specification framework, which allows the specifier a choice of two languages: Communicating Sequential Processes (CSP) [Hoa85] and a version of Propositional Temporal Logic (PTL), derived from [Eme90]. CSP is a process-algebraic language designed for the specification and analysis of parallel systems and (our version of) PTL is a real-time temporal logic designed to capture time-dependent constraints concisely. The behaviour of a CSP process is dependent on its environment; it is therefore difficult to assert global properties. PTL can be easily used to express global timing properties of systems, but it is less suited to describing the purely behavioural aspects. We will therefore develop a framework in which a specification is a pair (P ; OE), where P is a CSP process and OE is a formula of PTL. Global and timing constraints can be described within PTL, and behavioural constraints can be described within CSP. Both components of a specification have to be checked for mutual consistency, to do this we present a common semantic framework for both PTL and CSP. Since we wish to retain all the behavioural and all the timing information in this mapping, we choose to use a real-time CSP semantic model. However, the existing real-time CSP models [Ree88, Sch92, Dav93] insist that recursive processes must be time-guarded, that is some time must elapse between any instantiation of a process and its recursive invocation. This facilitates the task of semantically defining recursive processes, but goes against the philosophy of the dual language style which we develop here. We therefore present in Section 2 a novel denotational model for CSP (which we cal