A core calculus for correlation in orchestration languages

We introduce a formal framework for studying the mechanism of correlation in orchestration languages for Web Services. A core calculus based on typical process algebraic constructs is developed, enhanced with two mechanisms: (i) a management of scopes keeping track of variables, properties, and their assignment to values, and (ii) a construct to spawn service instances handling (cor-)related operations and guaranteeing consistent routing of messages. By abstracting away from low-level details of orchestration languages, this model can be used as a foundation for the correlation mechanism, paving the way towards the analysis of properties and the design of extensions and improvements. As an example application, we show how the calculus introduced can be extended with few imperative and control-flow constructs reaching the expressiveness of a significant fragment of BPEL orchestration language.