Changing System Interfaces Consistently: A New Refinement Strategy for CSP||B

This paper introduces action refinement in the context of CSP‖B. Our motivation to include this notion of refinement within the CSP‖B framework is the desire to increase flexibility in the refinement process. We introduce the ability to change the events of a CSP process and the B machines when refining a system. Notions of refinement based on traces and on traces/divergences are introduced in which abstract events are refined by sequences of concrete events. A complementary notion of refinement between B machines is also introduced, yielding compositionality results for refinement of CSP‖B controlled components. The paper also introduces a notion of I/O refinement into our action refinement framework.