Concurrency and Refinement in the Unified Modeling Language

Abstract

This paper shows how a formal notion of refinement may be defined for models, and model components, expressed in the Unified Modeling Language (UML). A formal, behavioural semantics is given to combinations of class, object, and state diagrams, using the notation of Communicating Sequential Processes (CSP); this semantics is adequate for the analysis of concurrent, communicating behaviour, and induces a notion of refinement for UML based upon existing notions of traces and failures refinement for CSP.