Theoretical Foundations of Scope-Based Compensable Flow Language for Web Service

Web Services have been becoming more and more important in these years, and BPEL4WS is a de facto standard for the web service composition and orchestration. In this paper, we propose a language BPEL0 to capture the important features of BPEL4WS, with the scope-based compensation handling mechanism, which allow the users to specify the compensation behaviors of processes in application-specific manners. The formal operational semantics of BPEL0 is given, with some key concepts related to compensation handling, i.e., the compensation closure and compensation context. Based on the semantics proposed, a new bisimulation called n-bisimulation is proposed, which is used to define the equivalence between BPEL0 programs. At the same time, some examples are presented to illustrate how the semantics works and to unclose the relationship between BPEL0 and BPEL4WS.