A Framework for Generic Error Handling in Business Processes

Recently the term Web Services Choreography has been introduced to address some issues related to Web Services Composition. Several proposals for describing Choreography for Business Processes have been presented in the last years and many of these languages make use of concepts as long-running transactions and compensations for coping with error handling. BPEL4WS, the most accredited candidate for becoming a standard in Choreography, provides three different mechanisms for coping with abnormal situations: Exception Handling, Event Handling and Compensation Handling. The complexity of BPEL4WS makes it difficult to formally define this framework, thus limiting the formal reasoning about the designed applications. In this paper we advocate that three different mechanisms for error handling are not necessary and we formalize a novel choreography language, based on the idea of event notification as the only error handling mechanism. We can take advantages of this formal description in two ways. Firstly, this language represents by itself a proposal of simplification for BPEL4WS including an unambiguous specification. Secondly, an implementor of an actual BPEL4WS orchestration engine should implement simply this single mechanism providing all the remaining ones by compilation. Notably, the proposed framework is expressive enough to compare different solutions for managing long running transactions such as BPEL4WS and StAC.