A Compositional Semantic Theory for Service Composition

Service Composition refers to a popular modern software paradigm for building applications by combining distributed reactive components using the World-Wide-Web as the medium. The approach is characterised by the use of standardised protocols, languages and representations such as XML, which ensures that services are platform agnostic. Whilst the architecture is well understood for simple single-interaction services built in the style of classical procedures from the traditional programming paradigm, much discussion is still taking place with regard to more complicated, fully reactive services, where the consumer interacts in a stateful manner. The aim of this Thesis is to investigate the way in which composite Web services are built, and provide a useful semantic theory for service composition. Inspiration for this comes from several sources, including existing technologies such as WS-BPEL and WSMO, and the workflow patterns research, which defines a diverse collection of control-flow patterns which should be provided by a service composition language. My approach to service composition is based on Abstract Timed Process Calculus. Core to this approach is compositionality – a Web service model must be semantically decomposable to allow component manipulation. An Abstract Timed Process Calculus allows elegant modelling of component systems through a variety of synchronisation patterns such as isochronic broadcast. In this work I will seek to advance this area by constructing a novel timed process calculus which seeks to surpass previous calculi. This calculus will form the underlying meta-model for a semantic theory for a service composition language called Cashew-A. The semantic theory will be useful for both verification and execution of composite Web services.