In the early days of BPM (four or five years ago) everyone thought BPEL was the BPM standard, at least for runtime execution. Not long after, the importance of business-friendly process modeling came to the fore, and BPMN emerged as the standard for that. The mismatch between graph-oriented BPMN models, where you can route the flow just about anywhere, and block-oriented BPEL, where you can't, didn't seem to worry BPM vendors. After all, a model was just a model, a business requirements document in diagrammatic form. The BPEL designer would use the BPMN as business input to the implementation and go from there. Then a new concept emerged, the BPM Suite, which included process modeling, executable implementation, and BAM in an integrated toolset that promised the improved business-IT alignment and agility needed to cope with ever-changing business requirements. Suddenly the process model became more than a business requirements spec. It was actually the first phase of the process implementation.
No problem, said the BPEL vendors. We'll just generate skeleton BPEL from the process model, and use that as the starting point for the BPEL designer. Voila! Business empowerment! Business-IT alignment! But this notion of the interface between process modeling and implementation design as a one-way handoff was flawed from the start...
Having been in the roundtripping-is-dead camp for about a year, I now find myself having to confront this issue once again. In my BPMN training, for example, students want to know what strategies or patterns should they use in their BPMN diagrams that will fit well with their expected BPEL implementations. It's not something I expected to think about when I started. In the BPMN specification, there is an attempt to describe simple BPEL mappings for many diagram patterns, but it has been long recognized that certain patterns cannot be mapped in the ways described in the BPMN spec. BPMN tools that validate for BPEL export based on these simple mappings tend to give users a lot of validation errors if the BPMN is not drawn in strict block-oriented fashion...
Read the complete article by Bruce Silver, Intelligent Enterprise.
