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Re: [jwt-dev] About the JWT Model

Le Saturday 06 December 2008 02:52:09 Koen Aers, vous avez ÃcritÂ:
> >> What are the opinions of other contributors? (JBoss particularly)
> Hi all,
> Actually my personal opinion in this discussion is 'the simpler the
> better'.
>  From a 'drawing perspective' it doesn't really matter how much info
> the metamodel contains. We think that all the nodes can be expressed
> by one generic node type which contains a set of properties and a set
> of constraints on those properties.

Of course, and I was of the same opinion initially. Basically, in the model we 
may have only two elements : Node and Edges. The remaining parts can be 
roughly expressed by properties. On the other side, I have the feeling that 
we have to agree on a common set of basic elements at the model level that 
provide enough informations for any extensions/tools (especially simulators) 
and that guarantee as far as possible, the compatibility of all of them. 

I think that properties do not provide the required compatibility guarantee. 
The model does as far as it is consistent and self-sufficient. In the case of 
the leaf nodes (Fork and others), I think we have both redundant 
informations, and mis-enforcement: I mean, that the requirement of UML 
Fork -- only one incoming transition -- is not enforced at all in the model, 
but in the graphical layer (edit part). Therefore, I propose either to remove 
those nodes or to ensure those requirements are enforced (but I don't know 
how to do it in a simple, straightforward manner).

> An 'execution perspective' would add behaviour to this generic node
> type but that is of lesser importance for modelling (it is for
> simulation though).

Right, and we are quite concerned by those simulators. We expect any 
simulators based on JWT to understand any design based on JWT model.

> This is very close to what Marc describes earlier. I didn't take a
> close look yet, but as I understood it, aspects can take us a long way
> in that direction.

Of course, aspects can help for the actual implementation. But we are 
concerned on compatibility issues raised by the model.
Pierre VignÃras
Bull, Architect of an Open World TM
*BPM Team*, Bull R&D
1, rue de Provence
38130 Echirolles (France)
Direct Line: +33-4-76-29-74-06

*Orchestra*, The BPEL open source project: http://orchestra.ow2.org
*Bonita*, The XPDL open source project: http://bonita.ow2.org