Executable BPMN call for action

In BPMI.org Redux Ismael Ghalimi of Intalio calls for participation in a group to sort out a true executable BPMN. The tentatively titled BPMNLab looks to be a good practical approach to the issues.

• What consitututes executable BPMN?
• Are there useful BPMN flow patterns that cannot be translated into WS-BPEL? If so, how are they best dealt with to produce an executable?

After what has been a bit of sniping from the sidelines on my part, I would be happy to be involved in this effort.

The transformation to BPEL approach seems to me pretty sound. Here is a working language definition appropriate for the BPM domain that is capable of withstanding rigorous assurance testing. Why attempt to define another?

A few BPMN constructs may produce really ugly BPEL code, but who cares except for a few developers in Intalio and the like who have to develop the transformation code. The last thing that anyone in the real world should be doing is fiddling with the generated code. I am reminded of a very successful Unisys product LINC which developed totally unreadable and arguably inefficient COBOL code. In years of use, we had no more reason to look at the generated intermediate COBOL than the final machine level code.

Comply with the specification for BPMN

Bruce Silver in BPMN-BPEL in Perspective responds to the same article as I did here and raises the issue of compliance.

OMG could define a compliance spec for BPMN 2.0 - the elements,
attributes, and flow patterns that MUST be supported to claim BPMN
support. They have made some murky noises about it, but I haven’t seen
anything concrete yet. Since IBM and Oracle are driving the bus there,
it would make sense that that subset would have a defined mapping to
BPEL, but it would allow non-BPEL engines to be compliant as well.

That would be a healthy thing for the industry. But I’m not holding my breath.

I may be more used to specifications for computer languages (like FORTRAN, COBOL) than business process but I suggest that the specification for BPMN 2.0 itself should be what vendors comply with and not a separate compliance statement. Compliance statements from vendors will then effectively state what they have not achieved (yet). Purchasers and consultants can then judge whether the level of compliance of a particular product is sufficient for there purpose.

As BPMN is unlikely to stop at 2.0, a really supportive vendor should not only be compliant with the currently approved specification but also support proposals for future versions, so that practitioners can work with the new ideas while they work through the acceptance process of a standard.

Execution is a different issue. A vendor could opt for a BPEL execution engine (as Intalio uses at present) and reflect that decision by flagging bits of the model as not-executable. An organisation working from the compliant BPMN model could than decide on a method for implementation ...

• use a tool that will generate an executable directly from the model, or
  
• hand the model to an IT developer as a requirement specification

I will be looking for solutions in the first category but we must not lose sight of the fact that a vast number of organisations like to keep a developer shop and consultants busy re-inventing processes in Java or whatever language is the flavour of the month.

Even for Intalio, the execution engine could be replaced by something easier to map to BPMN without changing the user view.

To BPEL or not to BPEL

In Why BPEL is not the holy grail for BPM, Pierre Vigneras thoroughly covers the issues of using BPEL as the implementation layer of a business process solution. From the article conclusions ...

• Therefore, we consider BPMN notation as the only currently viable solution for Business Analysts
• Transformation from BPMN to (readable) BPEL is quite hard to implement, and produces --- when correct --- hardly readable code.
• Therefore, we may wonder why BPMN is transformed to BPEL since there
  exist a graph-based standard that maps directly BPMN constructs ---
  namely XPDL v2.0
• Of course, one may claim that XPDL 2.0 lacks some execution specifications that makes him (sic) unsuitable for direct execution.

Although I am generally a fan of Intalio, Pierre provides a good example of the problems they get when BPMN is used as though it is a convenient graphical expression for BPEL. In particular, a real business analyst can express the process in valid BPMN which is then transformed by Intalio into BPEL which bears little relation to the designer's intention. Worse, the Intalio developers have removed valid BPMN constructs from the business analyst, probably because they do not readily fit with the BPEL implementation. To add insult to injury, there is a general impression that if your valid BPMN does not work, you must have designed your process against some mystic best practice rather than expressed real business events and activities.

I am less concerned about the round-trip issue. If the BPMN is transformed by a product into an execution language which then remains untouched by human developer hand why we should care about the readability of that executable code? The answer is that the maturity of product development in BPM does not give users much faith that the generated code will do what we expect.

If we concentrate on developing BPMN into the way of real business analysts express the business processes and assume an automatic transform into a executable, the choice of implementation paths is only of concern to product developers. Out in the real world we can judge their products by the ease with which we can describe the processes that we find (as-is) and design (to-be).