[jbpm-dev] [Design of JBoss jBPM] - Re: Defining the API Mission

[koen.aers@jboss.com]

"Ed" wrote : Re use of GPD... I'm pretty unhappy with GPD.  The code base is not very extensible, and is highly dependent on the XML editor codebase. 
I am sorry to hear that you are unhappy with GPD. But as a matter of fact I know its limitations and I am not that happy with it myself.
The current code is indeed very dependent on the XML editor. The reason for this is  a combination of history and the initial goal of providing support for the developers to edit the XML file. 
As for extensibility, as Matthew and others have shown, it is doable but there are indeed some quirks that have to be overcome. However, the input that came from users that extend the GPD has been very valuable to make this mechanism somewhat better.
"Ed" wrote : I went to the talk by the Eclipse BPMN editor guys at EclipseCon, and was very sold on GMF.  The BPMN editor is really slick, and easily extensible.  People kept complimenting them on this or that feature, and they kept saying things like "well, it wasn't really a requirement, but all we had to do to implement it was write these 5 lines of code, so we just threw it in."  High praise for the framework!
I have looked at the BPMN editor and it is indeed a very nice piece of work. However, its approach has a number of issues that I haven't been able to solve until now:
- serialization of XML compliant to our jPDL XSD
- graphical info serialized in another file or not
- easily integrate with an XML editor to edit the serialized XML
GMF builds on top of EMF and while I have been able to build small prototypes that come close to what we want, I still haven't been able to walk the final mile. I will open up a different topic with some of the results of my research. Maybe some people are able to help out with closing this final gap.
"Ed" wrote : After spending some time with the code, I am even more sold.  I would very strongly suggest that Koen look at GMF et al again - it's probably grown up a lot since he checked it out the first time.
I definitely agree with you that GMF has become better in the meantime. I have checked it out again after the last EclipseCon as well. Maybe I am still missing things, but as I stated before I still have problems in making it do what I want it to do.
So after a discussion with Kris Verlaenen (from the Drools team) around the effort to implement a common base for a 'flow' editor we have decided to not use GMF for this (the high dependency of GMF on the very intrusive EMF framework was a real breakpoint for Kris). As a plus, this new effort will be highly focused on extensibility. Anyway, if we have been looking past important things, we are open to suggestions. As already said, I will open a different topic with the ideas and research results that I obtained earlier.

Regards,
Koen

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