Transforming dynamic behavior specifications from activity diagrams to BPEL

The Service-Oriented Architecture (SOA) provided by the Web Services standards supports Model-Driven Development, it allows global business process models described in the Business Process Modeling Notation (BPMN) or as UML Activity Diagrams to be transformed into Web Services components specified by WSDL and/or BPEL. We have experimented the transformation of UML Activity Diagrams to several BPEL processes using the IBM Rational Software Architect (RSA) tool. These diagrams were derived from the specification of global system behavior where each activity may represent some collaboration between several system components in distributed systems. The derived component behaviors assure that the global behavior will be realized by coordinating the actions of the components through the exchange of asynchronous messages. In this paper, we describe how this method can be adapted to the context where the system components will be implemented as BPEL processes. We found out that the IBM Rational tool does not support some important asynchronous message exchange scenarios, and we describe here how the generated BPEL processes can be manually adapted. We also discuss some difficulties that arise in relation with input message buffering. since we assume that the received messages remain in a buffer pool until they are required by the destination process. This message buffering is largely provided by the BPEL execution environment. We explain in this paper how all these problems can be resolved by simple modifications of the automatically generated component behaviors in BPEL.