For you who read this blog on occasion, please help. I am looking for any valid BPMN diagrams that can not be represented as standard XPDL. Many people understand that XPDL is a superset of BPMN, meaning that everything from BPMN can be represented as XPDL, while the converse is not necessarily true. There are, however, a few vocal opponents who claim that XPDL can not be used to store BPMN.
OK. Both BPMN and XPDL are complex subjects. I know that when creating the XPDL 2.1 specification, a detailed examination of the BPMN spec was made, and every attribute of every element was accounted for in the XPDL file format. It is possible that one was missed, and it is possible that there are combinations of things that somehow can not be represented. While I doubt this is the case, I have an open mind for discussing the possibility.
What I need from you: Can anyone identify a BPMN diagram that can not be expressed as standard XPDL. I really want to know if any such diagram exists.
No extended attributes necessary: XPDL has an extended attribute mechanism, so of course XPDL could be used to represent anything, but to keep things fair, I am only talking about standard XPDL elements that are fully defined in the XPDL spec. There must be a standard way to represent the BPMN diagram, and if you can identify a BPMN diagram that requires extended attributes, then that counts as well.
Anything in the BPMN Spec: The current BPMN revision is 1.2, and so any element defined by that spec can be included as long as it is used in the way that that specification defines as proper use. Naturally, vendor specific extensions to BPMN may require extended attributes in XPDL, but this challenge should avoid proprietary extensions of either standard.
That is it. If you can draw any valid BPMN diagram that can not be represented as standard XPDL, I will write a follow on post discussing the gap. Write a comment, or let me know how to contact you to get the graphical image. Thanks in advance. 🙂
Thinking Matters 
George Lawton wrote an article about the same time that this one was written called “Co-evolution of BPMN and BPEL drives BPM in SOA settings”.
He says
“But challenges remain in translating business models built in BPMN into applications written in BPEL.”
“There are concepts in BPMN that don’t exist in BPEL.”
“For example, if BPMN-to-BPEL round-tripping allowed companies to avoid vendor lock-in, maybe this could be a payoff. But I have yet to see vendors keen in moving towards interoperability. Even interoperability between BPMN tools or between BPEL tools is problematic.”
I am fairly convinced at this point that nobody knows of any BPMN diagram that fails to be serializable as XPDL. I have talked to a number of the vendors who implement such tools, and nobody could come up with any examples that can not be saved as XPDL.
I mention this only because there are a couple of fanatics out there that make vague and unfounded claims to the contrary. Please be wary of them.
I have a question in this discussion:
Can XPDL handle multiple instances of elements. I’m working in a BPM modelling tool with XPDL support. The tools supports creating multiple instances of eg. lanes, sub-processes, etc. The problem is that they claim that XPDL does not support multiple instances. So when I export the model to XPDL, the model only keeps one instance of the elements. This results, off course, in a totally unreadable model (all links to the multiple instances now link to the single remaining instance).
Now my question is: is my vendor wrong and should they adapt their XPDLscripts to support multiple instances or does XPDL lacks support to multiple instances?