Standardizing the Right Thing: BPMN or BPEL?
Thursday, June 29, 2006
Creating portable process logic is certainly a good thing. Today, most of the focus for doing this is on BPEL, an executable language for describing processes. As I've argued before
, BPEL currently falls short of this goal. Yet even if it didn’t, is BPEL really the right thing to standardize?
Think about the goals we’re trying to achieve. Portability of process logic, the ability to move implementations from one platform to another, is certainly one of them. But portability of people, allowing us to move our skills from one process design tool to another, is also important. BPEL can potentially help with the first goal, but it’s not appropriate for the second; the majority of people who create processes will never work directly in this complex XML-based language. Instead, BPEL is typically generated from some graphical process description. The emerging standard for specifying processes graphically is the Business Process Modeling Notation (BPMN)
. If BPMN becomes widely supported, as seems possible, it will make people’s process design skills portable.
So wouldn’t it also make sense to use BPMN as the foundation for making the process logic itself portable?The most recent version of the XML Process Definition Language (XPDL)
, created by the Workflow Management Coalition
, defines a way to do this. By specifying a standard XML file format for representing serialized BPMN diagrams, XPDL 2.0 provides a way to move process logic between different environments. Assuming that we can express everything we need to say about an executable process in BPMN--something that's at least a small leap of faith—why should anyone care about BPEL? BPMN and the standard representation provided by XPDL 2.0 can achieve both portability of people’s skills and portability of the process logic those people create. Who cares what language is ultimately used to execute that logic?
There are some challenges in making this a reality, of course. BPMN isn’t yet fully supported, especially by the major vendors, nor is the XPDL 2.0 serialization of BPMN widely used today. Also, although it was created elsewhere, BPMN is now owned by the Object Management Group (OMG)
. Producing straightforward, usable standards in a timely manner hasn’t been OMG’s forte, so I can’t help worrying a bit here. Also, OMG is hard at work creating a Business Process Definition Metamodel (BPDM)
that, among other things, is meant to provide an alternative to XPDL for conveying serialized BPMN diagrams.
Given all of the vendors and standards organizations involved, the most likely outcome is probably a mishmash of partially supported standards, with users left paying the price. Still, the goals are clear: portability of both people’s process design skills and of the process logic they create. Focusing on the graphical process definition notation can address both of these areas. Fully standardizing BPMN, complete with a standard file format, seems likely to be a better solution than standardizing just an executable language such as BPEL.