FW: [sca-assembly] ISSUE 2: Use of UML 2.0

It looks like my subscription is finally working, apologies if I sent this twice by accident, or if these comments are coming late...

I just wanted to give my feedback on a couple of points raised here...

Mike wrote:
>Second comment: Why did the SCA specifications use their own form of Diagram?
>This was the original question raised by Jeff Estefan, who said in effect "why not use UML 2.0 diagrams?"
>I think that the basic reason that the SCA specifications have their own diagrams rather than using UML 2.0 is that SCA isn't UML.
>I hope that this does not come across as too dismissive or too glib, but I think that Jeff Anderson's efforts building SCA
>diagrams using UML 2.0 actually help prove the point.
>SCA has its own concepts, its own semantics. Some of them map well to UML 2.0, some not so well.

>It is possible to regard SCA as a kind of domain specific language, which can (partly) be derived from
>a UML model of an SOA system. A mapping is possible from UML to SCA - we have had that debate with
>UML supporters in the past, and I don't think anyone would argue against that.

>However, SCA is actually an executable language and in this regard it does go further than UML.

I was hoping that my diagrams would prove the contrary, I guess that beauty is in the eye of the beholder :-)
while it is true that SCA is a domain specific executable language that has its own concepts and semantics, the same can be true of almost any technology based on a particular specification. EJB's, AOP, JSF, WSF, etc. all have particular extensions and approaches that can make fitting them into UML less than straightforward. I think that if each one of these technologies/approaches had a different diagramming notation things would get complicated very quickly. In my opinion an easier approach is to adapt UML to SCA especially since UML has such a rich component diagramming notation, most modeling tools support it , and it has become somewhat of a standard. Many of the topics that have not yet been addressed within the SCA diagrams such as complex properties, relationship cardinality, inheritance etc. already been addressed within SCA.

Mike Edwards wrote:
>Third Comment: Do the SCA diagrams need to be normative?

>This is a different question, but it is lurking here, so we might as well get the debate into the open.

>I think that there are some advantages to having a "standard" form of diagram for SCA. Basically, it
>will help end-users if the same things are rendered in the same ways, whether they are looking at a book,
>using a programming tool or viewing a web page.

>So, I argue that the SCA diagrams should be normative but optional. They are definitely part of the specifications
>and where the specs require diagrams they should all be in the one form. It should be strongly suggested that
>tools (etc) relating to SCA should use this form of diagram, to avoid confusion. However, folk are not forced to
>use them if there are good reasons not to do so....

I agree with this approach, forcing any diagram notation is never a good idea, whether it's SCA or UML. Furthermore, will believe this is an interesting topic, am very interested in a robust normative notation for SCA, it's probably not the number one priority for the SCA technical committees in general. We'll probably want to shake down and stabilize the specifications, before we go into too much more detail about how these specifications should be represented. The current diagrams we have now are doing the job that they need to.

Jeff

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