Enterprise Architect vs. Service Architect

If you open any book on SOA you find it defined as an architecture which offers a framework for improved business - technology alignment. In [1] SOA is defined as "a framework for integrating business processes and supporting IT infrastructure as secure, standardized components - services - that can be resused and combined to address changing business priorities". The IBM SOA Foundation [2] defines SOA as "the practice of deriving an information system design from a business design".

I find both definitions to be confusing and incomplete. The first definition is basically an enterprise architecture (EA) framework, right? The definition that it is a framework means that it defines governance, perspectives (views) and/or some methodology. Similar to TOGAF, or Zachman (does not have a methodology) or other well known architectural frameworks. TOGAF which is a framework for enabling the design, evaluation and build of the right architecture for an organization [3] offers an enterprise macro level architectural definition. TOGAF defines four main domains - business, data, application and technology. Well, the answer is not quite right. SOA is not EA, SOA is applicable at a level lower than the enterprise, it is focused on the service level, wherever it might be. In some cases services could be enterprise-wide and high level, but most of the time it is local.

Lets think of SOA as the "service instantiated" architecture for an enterprise architecture. To make it easier to understand lets take the example of a small non-profit community center. An enterprise architecture for this community center is the evaluation, definition, design and build of an integrated structure unifying the community center to allow it to achieve its mission. For example an enterprise staff appraisal system as part of that architecture. On the other hand SOA will define how the various services related to a staff performance system can be designed in IT resources and aligned to the business goals. Services could be "Staff Feedback Solicitation", "Performance Appraisal Metrics Definition", "Performance Appraisal Metrics Assessment", and several more. So in a sense SOA is addressing the question of "now we have an enterprise wide structure and method to appraise staff performance, how can we actually turn it on, and customize it for different departments, with optimum reusability of approaches and resources.

Other definitions of SOA is that is it is "a methodology and approach that can be utilized to deliver or to support an enterprise architecture initiative" [4].

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[1] Norbert Bieberstein, Sanjay Bose, Marc Fiammante, Keith Jones and Rawn Shah, " Service-Oriented Architecture (SOA) Compass: Business Value, Planning and Enterprise Roadmap, IBM Press, 2006.

[2] Rob High, Stephen Kinder and Steve Graham, "IBM's SOA Foundation: An Architectural Introduction and Overview", IBM Business Consulting Services, Version 1.0, Nov 2005.

[3] The Open Group, "The Open Group Architectural Framework (TOGAF)", Version 8.1.1, Enterprise Edition, 2007.

[4] Niel Maehiter, Quote in an Article titled, "What's the difference between SOA and enterprise architect?" by Joe McKendrick, June 11th, 2007. (link)

Is there a difference between a SOA repository and a SOA registry?

Generally speaking a registry is a location that stores information about registered entities. A few of examples of registries could be a town's birth registry which records all births in the town, a College class registration office, and an annual article index of a publication which lists all articles that appeared in the publication during a particular year.

Registry is defined in the Webster's College Dictionary as the "place where a register is kept", and the dictionary defines register as "a book in which records of events, names, etc., are kept".

In the examples provided above we see that the birth registry will contain a list of all names of people who were born in the town, their dates of birth and maybe some other information like the address at the time of birth, ages of parents, names of parents, etc. We do not expect to see the actual people in the registry ! The people will be in their offices, homes or wherever else.

Similarly, in the case of the annual article index, which is another form of registry we expect to see the titles and dates of publication of articles that appeared in the publication during that year. We do not expect to find the articles themselves in the index of articles.

A repository on the other hand is a location where actual artifacts are stored. We can guess that for the example of the birth registry, the actual repository would be hospitals, delivery clinics and places where people give birth. This is where we can actually find the babies.

Similarly in the case of the article index, the actual articles would be find in the various issues of the publication throughout the year, and would be stored in a library.

Repository is defined in the Webster's College Dictionary as " a place where things are deposited, stored or offered".

So now in the context of SOA, we can define the Service Registry and Service Repository as follows.

Service Registry
A comprehensive list of all SOA services available to an enterprise to achieve a business objective. The list would include the service identification information, location of the service, service classification (purpose), and information about how to interact with the service.

Service Repository
A storage location that houses the SOA service and its components, is involved in controlling access to the service and the presentation of the service to its users

If we ponder for a moment we notice that some key areas of a SOA service are neither part of a service registry or service repository - at least by defintion. For example a service's history, statistics about the the service, performance reports, etc.. by definition are not part of the repository. Some SOA implementations or frameworks might decide to store such service management reports and information in the repository, others might wish to develop a SOA Service Management Repository which will house that kind of informaton.

Enterprise Architecture

Enterprise Architecture is the organizing of logic for business processes to reflect the integration requirements of an enterprise's operating model.

It is important to identify the processes, data, technologies and interfaces that are core to the definition of the operating model. Different enterprises will have different operating models and hence the focus on each of those mentioned areas would be different. For example a wholesaler in the oil industry will focus on processes and data more than a retailer in the finance industry whose focus would be on client data and interfaces.

Some artifacts that could be used as starting points to define an enterprise architecture could be functional architectural diagrams, which would highlight the main functional processes. Another artifact is an external interface diagram. A list of shared data and key technologies linking the various applications also serves as a good defining artifact.

Organize Your System: Architecture versus Framework

Architectures and frameworks are among many other artifacts that could be used for organization. So what is the difference between an architecture and a framework?

Architectures define a unified structure of a system. It is concened with the purpose determination, concept, structure, use and behavior of the system. Architectures could be physical, operational, technical or functional.

Frameworks define the data and information that needs to go into an Architecture. For example a framework will define that a functional architecture will include functions, inputs and outputs of these functional blocks, controls and maybe actors performing these functions.

Common frameworks are DOD Architecture Framework (DODAF), The Open Group Architecture Framework (TOGAF), Federal Enterprise Architecture Framework (FEAF), and they define what needs to be in a C4ISR Architecture, Enterprise Architecture and a Federal Enterprise Architecture respectively.

More to come on this topic soon...