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Understanding SOA Architectures and Models - Part 2

The SOA reference architecture

While there are SOA reference architectures all over the place, including mine, the best known SOA reference architecture is defined by OASIS. Here is their definition, albeit a work in progress:

"A reference architecture is a description of how to build a class of artifacts. An architecture describes how to build a particular artifact. The appropriate way to write the description for a reference architecture depends on the particular artifact. For example, you could describe the properties of the artifact. Another way is to write a set of steps (e.g., a recipe) for building the artifact. You could decompose the artifact to an appropriate number of components and subcomponents.

The SOA reference architecture (RA) provides a bridge between the concepts and vocabulary defined by the SOA Reference model and the implementation of a SOA. The SOA reference architecture models the abstract architectural elements for a SOA independent of the technologies, protocols, and products that are used to implement a SOA. Some sections of the RA will use common abstracted elements derived from several standards."

I have to agree with this, albeit it is a bit confusing. They are describing a high level of abstraction to define a SOA, the "reference architecture," and the "architecture" as an instance of a SOA. I get that. However, the larger issue is the fact that the problem domains I'm seeing are not as similar as you think, thus the question is: Can you define a single class of artifacts, and thus provide a sound "jumping-off-point" for the instance? I think a few use cases will prove this out. I could not find many, so send them to me if you have them...I'll post them here. However, to be fair to the creators of the standard, this is still a work in process.

Also confusing is the number of SOA reference architectures you see out there, including this one from Web Methods:

What's more, you can find more vendor-created models going by different names, but basically attempting to define the same thing...a reference architecture for SOA. However, most appear to define the same notions as put forth with the SOA Reference Model (discussed next).

Here are some others:

Some of the key issues, as I see it, are:

There really needs to be some fundamental discussions about the use of the Reference Architecture and the Reference Model in the real world. Based on what I found out, as an outsider, there seems to be an impedance mismatch between the way the architecture and model is defined and what's currently going on in the world of SOA. I'm assuming that will "self correct" over time.

It's unclear as to how all of this reaches up into the domain of the enterprise architecture...perhaps not as a replacement, but an augmentation. If so, how do we approach that considering the other frameworks employed?

Like many written standards, the approach is somewhat confusing. Not that the standard itself is bad. I don't think that's the case; but it's difficult for those tasked with building a SOA to see how it will mesh with their current architecture and their current thinking. Over the years I've found that to be as important as good concepts.

More Stories By David Linthicum

Dave Linthicum is Sr. VP at Cloud Technology Partners, and an internationally known cloud computing and SOA expert. He is a sought-after consultant, speaker, and blogger. In his career, Dave has formed or enhanced many of the ideas behind modern distributed computing including EAI, B2B Application Integration, and SOA, approaches and technologies in wide use today. In addition, he is the Editor-in-Chief of SYS-CON's Virtualization Journal.

For the last 10 years, he has focused on the technology and strategies around cloud computing, including working with several cloud computing startups. His industry experience includes tenure as CTO and CEO of several successful software and cloud computing companies, and upper-level management positions in Fortune 500 companies. In addition, he was an associate professor of computer science for eight years, and continues to lecture at major technical colleges and universities, including University of Virginia and Arizona State University. He keynotes at many leading technology conferences, and has several well-read columns and blogs. Linthicum has authored 10 books, including the ground-breaking "Enterprise Application Integration" and "B2B Application Integration." You can reach him at [email protected] Or follow him on Twitter. Or view his profile on LinkedIn.

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