Understanding SOA Architectures and Models…SOA RM

A few people who have been reading my blog and listening to my Podcast, as well as reading other SOA blogs and articles, have become a bit confused pertaining to the notions of:

– SOA Reference Model(s)

– SOA Reference Architecture(s)

And how all of this works and plays with

– Enterprise Architecture

In fact one of those creating the standard, NASA JPL’s Jeffrey A. Estefan, who responded to a past blog post, assisted me in fact checking this series of posts since some of this information was a work in process, and Jeff has better context as an insider.

So, I spent a few hours of my weekend attempting to research and define these concepts a bit better, in essence, taking everyone’s opinions and normalizing them so they make better sense. What I found were many of the same notions, defined differently, but all attempting to solve the same problems. Seems to be a common theme within the world of SOA…but I digress.

Indeed, there are many definitions for the above concepts (not those terms specifically), that are now being defined by guys like me, standards organizations such as OASIS and the Open Group, and vendors such as IBM, BEA, webMethods, and TIBCO. Sometimes they align; most of the time they don’t.

So, who’s right? I’m not sure this is a matter of right and wrong, but perhaps it’s time we come up with some common definitions and shared vision, as I’ve been saying. I do think we are moving in that direction, albeit slowly, and I think that just agreeing on semantics will be a huge accomplishment in this emerging space.

I’ll tell you what I know; you can make your own choices. Let’s begin by exploring the concepts being put forth by the standards organizations over the next several blog-days. This will be backing up a bit from the recent posts and columns that have basically restated and commented on the news…I’m attempting to provide better context.

Also, to avoid the many e-mails and comments I get when writing about this stuff from those who write the standards and define these terms, I’m going to be quoting more than I typically do. Of course, I have to add my 2 cents. Here goes…

SOA Reference Model

First let’s explore the concept of the SOA Reference Model, also a product of OASIS, and how SOA Reference Model and SOA Reference Architecture relate to each other. I’ll talk more about the SOA Reference Architecture in my next post.

From the OASIS Reference Model for Service Oriented Architecture.

“A reference model is an abstract framework for understanding significant relationships among the entities of some environment. It enables the development of specific reference or concrete architectures using consistent standards or specifications supporting that environment. A reference model consists of a minimal set of unifying concepts, axioms and relationships within a particular problem domain, and is independent of specific standards, technologies, implementations, or other concrete details.

As an illustration of the relationship between a reference model and the architectures that can derive from such a model, consider what might be involved in modeling what is important about residential housing. In the context of a reference model, we know that concepts such as eating areas, hygiene areas and sleeping areas are all important in understanding what goes into a house. There are relationships between these concepts, and constraints on how they are implemented. For example, there may be physical separation between eating areas and hygiene areas.

The role of a reference architecture for housing would be to identify abstract solutions to the problems of providing housing. A general pattern for housing, one that addresses the needs of its occupants in the sense of, say, noting that there are bedrooms, kitchens, hallways, and so on is a good basis for an abstract reference architecture. The concept of eating area is a reference model concept, a kitchen is a realization of eating area in the context of the reference architecture.”

Furthermore:

“The goal of this reference model is to define the essence of service oriented architecture, and emerge with a vocabulary and a common understanding of SOA. It provides a normative reference that remains relevant for SOA as an abstract and powerful model, irrespective of the various and inevitable technology evolutions that will influence SOA deployment. The concepts and relationships defined by the reference model are intended to be the basis for describing references architectures and patterns that will define more specific categories of SOA designs. Concrete architectures arise from a combination of reference architectures, architectural patterns and additional requirements, including those imposed by technology environments.”

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

I would, however, recommend that OASIS make this a bit easier to understand for the typical end user, as I stated before. Jeff sent me the graphic attached to this blog, which helps in figuring out the relationship between the reference model and the reference architecture (discussed in my next blog). Again, perhaps provide published use cases for the RM and RA, and thus make the notion a bit more consumable. I’ll consider this an open-ended definition for now, so please send your use cases and I’ll post them here. In essence, how the reference model will be used in a sentence.

You have to give them an A for effort, but you can see where debates such as the one I blogged about 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. I’ve been building that recently, and I’m happy to map them back to this reference model if it makes sense for the project. The uses cases out there are like snowflakes, and one size, or one model, does not fit all. You have to account for that within all this formality.

However, to be fair, if you Google “SOA Reference Model” or “SOA Model,” or things of that nature, you’ll find that most SOA vendors and consulting organizations have their own SOA (reference) models, SOA frameworks, SOA Roadmaps, or SOA reference architectures. They are a bit different than what OASIS is proposing, but again, looking to solve the same sets of problems.

My best advice is to leverage the architecture, models, roadmaps, or frameworks that will work best for you. At the end of the day, I think clarity of approach will win over complexity, as long as you can do that without diminishing the value.

Next, we’ll talk about the SOA Reference Architecture in more detail.