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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
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