Wednesday, May 02, 2007

David Linthicum gets SOA - a good read.

I have just read an article by David Linthicum on SOA Reference Models and Reference Architectures. David has explained how the two relate to each other very well and I consider it a good read. There are a couple of points he makes that I am also wanting to expand upon.

In David's blog post, he writes:

"Again, abstraction, one is an instance(s) of the other, if I understand this correctly."

This infers that the SOA Reference Architecture work at OASIS is an instance of the SOA Reference Model. While close, this is not quite accurate. The OASIS Reference Model for SOA is in fact abstract. By definition, an abstract entity cannot have instances, the same definition shared by UML 2.0 and programming languages like Java. The relationship is best described as the Reference Architecture "is based" upon the Reference Model. The OASIS SOA RM TC always knew that there would be multiple SOA works (architectures) based on the Reference Model. Such is the purpose of a model, to allow various architectures to be based upon it which maintaining a common language and understanding of the core concepts, axioms and relationships.

David also writes:

"I urge you to download and read this 31-page document to get some additional details. Also, get involved, if you like. I always love the comeback from standards bodies that deal with criticism and debate around the concepts they put forward: "If you don't like it, join us and change it." Can't argue with that."


"You have to give them an A for effort, but you can see where the debates are going to pop up. It's really a matter of understanding, a marketing issue really. I understand different levels of architectural abstractions, but what is really needed is a reference framework or model, and a set of steps to figure out how to build something that's proper for your problem domain."

David correctly notes the true purposes of a reference model here. Even if you disagree with it, it is a point of reference a person can use to explain their variances in definition. For example, if someone claimed that SOA was not what the reference model stated, they have a point of reference for their definition. As such, there will likely never be newer editions of the RM work unless some great inconsistencies are uncovered during he RA works going on in various bodies, companies and vendors.

FWIW - I give David an "A" for his continued clarification of SOA. I'm adding him to my blogroll.

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