A Technical Comparison of XPDL, BPML and BPEL4WS

1 Introduction XML-based business process languages represent a new approach to expressing abstract and executable processes that address all aspects of enterprise business processes, including in particular those areas important for web-based services. In this paper we focus on a comparison of three XML business process languages. We will compare the Business Process Management Initiative's BPML, XPDL, the WfMC proposed standard, and the new standard proposed by IBM, Microsoft and BEA, BPEL4WS, hereafter abbreviated to BPEL. Microsoft's XLANG and IBM's Web Services Flow Language (WSFL) were earlier variations that were combined in BPEL4WS. Our primary objective is to clarify the differences between the BPML , BPEL and XPDL paradigms. We are interested in exposing what can be done with one language and cannot be done, or done only with difficulty in the other. When simple extensions are possible, we propose them. We are also concerned about the work being done by three standards organizations: • WfMC (Workflow Management Coalition) • OMG (Object Management Group) • BPMI (Business Process Management Initiative) BPMI has also proposed a common modeling notation (BPMN). The comparison of BPML and XPDL should expose some of the challenges in this undertaking. In a joint meeting on November 19, 2002 BPMI invited WfMC to specify additions to BPMN that would allow it to serve as a graphical front end to XPDL. OMG has not been directly involved in the BPMN project. • Defines the behavior of Web service interfaces