A CSP approach to Control in Event-B

Event-B has emerged as one of the dominant state-based formal techniques used for modelling control-intensive applications. Due to the blocking semantics of events, their ordering is controlled by their guards. In this paper we explore how process algebra descriptions can be defined alongside an Event-B model. We will use CSP to provide explicit control flow for an Event-B model and alternatively to provide a way of separating out requirements which are dependent on control flow information. We propose and verify new conditions on combined specifications which establish deadlock freedom. We discuss how combined specifications can be refined and the challenges arising from this. The paper uses Abrial’s Bridge example as the basis of a running example to illustrate the framework