Chunks: Component Verification in CSP ∥ B

CSP||B is an approach to combining the process algebra CSP with the formal development method B, enabling the formal description of systems involving both event-oriented and state-oriented aspects of behaviour. The approach provides architectures which enable the application of CSP verification tools and B verification tools to the appropriate parts of the overall description. Previous work has considered how large descriptions can be verified using coarse grained component parts. This paper presents a generalisation of that work so that CSP vertical bar vertical bar B descriptions can be decomposed into finer grained components, chunks, which focus on demonstrating the absence of particular divergent behaviour separately. The theory underpinning chunks is applicable not only to CSP vertical bar vertical bar B specification but to CSP specifications. This makes it an attractive technique to decomposing large systems for analysing with FDR