The chair of the Workflow Management Coalition, Jon Pyke, has refuted the suggestion in a recent Computer Business Review article that the WfMC’s XPDL standard has been a failure.
Pyke pointed out that to date there are over 50 major business process management and application vendors that support the XPDL standard, including IBM, Oracle, BEA, Fujitsu, Tibco, and Global 360.
Pyke argued that the Workflow Management Coalition’s XPDL standard, which is a standard for the storage and exchange of business process diagrams, is often incorrectly perceived to be competitive with the business process execution language, BPEL, standard.
There are only three key standards to really take notice of [in the business process modeling and notation space], he said. They are BPMN, XPDL, and BPEL. But just having three to focus on still manages to cause some concern and confusion.
Business process modeling notation is a standardized graphical notation for drawing business processes in a workflow, Pyke said. BPMN’s primary goal is to provide a standard notation that is readily understandable by all business stakeholders. BPEL is an ‘execution language’, the goal of which is to provide a definition of web service orchestration, the underlying sequence of interactions and the flow of data from point to point.
As for XML process definition language, XPDL – a format standardized by the Workflow Management Coalition, WfMC – Pyke said its primary goal is to: store and exchange the process diagrams, or specifically to allow one tool to model a process diagram, and another to read the diagram and edit, another to ‘run’ the process model on an XPDL-compliant BPM engine, and so on.
The XPDL file can provide this design interchange because it offers a one-for-one representation of the original BPMN process diagram, said Pyke. It can be written and re-read to recover the original diagram.
BPEL, by contrast, is a non-trivial mapping, which is widely recognized as being one-directional, Pyke said. You can take a BPMN diagram and produce BPEL, but it is difficult or impossible to recover the original BPMN diagram from the BPEL. This is not surprising since BPEL was not designed for process design interchange.
For this reason, Pyke added, XPDL is described not as an executable programming language like BPEL, but specifically a process design format that literally represents the ‘drawing’ of the process definition.
Pyke was adamant that XPDL in no way competes with BPEL, and for that reason to compare the relative levels of support for one over the other is to miss the point. There is a general misconception that these two standards are in some way competing with one another but the reality is entirely different: BPEL and XPDL are complementary standards and easily coexist, he told Computer Business Review.
Pyke also pointed to a recent comment by Keith Swenson, Fujitsu Software chief architect and WfMC vice chairman Americas, who when asked recently which file format should be used by a business that wants to preserve its investment and ensure stored processes would be readable in the future, responded: XPDL is the only standard XML diagramming format supported today by dozens of vendors, and likely to be supported by tools in years to come.