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A Classification Scheme for Defining SOA

A way of breaking the big SOA beast into smaller digestible pieces

Since its inception, the term “Service-Oriented Architecture” - SOA - has confused and befuddled the masses. Those that believe they are doing SOA are sometimes told they are not, but their critics are unable to point to clear reasoning for their comment. Some believe that you can buy a toolkit for SOA, while others say that is nonsense; just an abuse of the term for marketing purposes by vendors.

Clearly, the word architecture is an explicit part of the term, yet it is discussed in lock-step with technological implementation strategy and efforts. Most importantly, many definitions of SOA exist without clear adoption of one over all others. Needless to say, the one thing we can all agree on is that there is confusion surrounding SOA.

One of the most problematic factors in providing clarity around SOA is that all definitions proposed seem to be expressed in the narrative. However, there is no effective narrative that can capture the essence of what SOA is today. That is, even though SOA may have been the brainchild of a few with a particular notion, the industry must come to agreement that SOA has taken on a life of it's own and the contributions of the many need to be aggregated together to form a cohesive and inclusive definition.

This article proposes an alternative to narrative SOA definitions that can be used to better scope and understand SOA initiatives, which will help to better rationalize SOA efforts with business goals. The SOA Classification Scheme allows the various aspects of SOA that have merit, even if they were not contemplated at origin, to be incorporated into SOA as a viable goal and to be related with the more traditional aspects of SOA.

A Common Value Proposition

Regardless of the class of SOA you subscribe to, there is a general underlying value proposition that is common to all classes: a means for independent objects to work together for a common purpose. When entities remain independent, but can work together, they can be used for multiple purposes, which makes them a better value than a “uni-tasker”.

Early works on SOA describe this design pattern as “loosely-coupled,” which represents that there is a temporary relationship between two elements as they work together, but neither is permanently bound to the other's existence nor are they limited to work only with each other.

A SOA Classification Scheme

  • Enterprise SOA Design

Enterprise SOA (ESOA) design deals with cross-cutting concerns related to business and technology. SOA principles applied to the ESOA design class is the most complex and comprehensive SOA initiatives. Ultimately, the output from the EA design class efforts need to become system, service or semantic design class initiatives in order for them to deliver value to the business.

It is this transition that is one of the biggest hurdles for SOA initiatives within organizations and a leading indicator of failure. However, as will be illustrated later in this article, failure is subjective and based on mismanaged expectations created by poorly-defined narrative definitions of SOA.

The primary benefit of undertaking an ESOA Design initiative is to create a master plan against which all systems will designed and integrated into the business. It helps to reduce redundancy by identifying similar requirements across the Enterprise. Moreover, the plan helps with planning and budgeting of systems.

  • System Design

The system design class deals with the holistic representation of elements as service providers and service consumers operating together to form both open and closed systems. This particular use of the term “system” is used to represent any group of independent objects working together for a common purpose. Hence, we could be discussing computer systems, but also traffic systems, highway systems and even a heating system.

    Application Design

    Application design is a subclass of system design. In the field of software engineering, where the idea of SOA was hatched, loose-coupling has become a mantra for IT leaders attempting to come to grips with overwhelming backlog, aging systems, complex integration requirements and limited numbers of trained staff. By applying the emerging concepts of self-describing software components, i.e. services, with domain-specific languages, application developers have created ways that they can speed development and leverage configuration as a means of modifying behavior versus code modifications.

    The primary benefit of the Application Design class initiative is to deliver greater reuse of software componentry and to facilitate more rapid development of solutions by leveraging existing software where ever possible.

    Infrastructure Design

    Infrastructure design is a subclass of system design that deals with making storage, memory, CPU, networking available as services, thus allowing these subcomponents to be pooled together on demand to meet the various requirements of the business. Cloud computing is an example of infrastructure design class.

    The primary benefit of the Infrastructure Design class initiative is to deliver greater optimization of existing infrastructure components, thus reducing the need for capital expenditures and reducing expenses.

  • Service Design

The Service Design class focuses on SOA as a business model, sometimes more quickly identified by its moniker Software-as-a-Service. This class is more concretely described by the elements of what a service offers, than by the nature of the interdependencies. Early works on Web Services, such as Loosely Coupled: The Missing Pieces of Web Services by Doug Kaye and Out of the Box: Strategies for Achieving Profits Today & Growth Tomorrow Through Web Services by John Hagel III and John Seely Brown, illustrate the concept that the Web is a portal through which many services are offered and consumed. It is an aspect of SOA that is less emphasized today than in the days when these books were penned. The primary benefit of the Service Design class initiative is to align the design goal with revenue generation.

  • Semantic Design

The Semantic design class focuses on meaning defined by service contracts. None of the other classes concerned themselves with the purpose or meaning of the services; just simply the domain in which they were applied. The semantic design class focuses on the alignment of the services with business. For example, the application design class may focus on the creation of data services. These services tend to be technical in origin and very generic. Whereas a service design within the semantic design class may focus on an aspect of business it represents, such as underwriting, trading or production.

The primary benefit of the Semantic Design class initiative is to express service contracts that mimic the activities of the business, thus allowing the service to modeled and automated in a consistent manner.

Examples of the Classification Scheme in Use

The classification scheme is just a tool to help businesses that have SOA investments to do a better job rationalizing their efforts and demonstrating forward progress and benefit in spite of the complexity and hardships associated with the initiative. The classification can also be used as a tool by companies seeking the benefits of SOA, but without full understanding of how and where SOA can be applied effectively within their business.

The following are some examples of the SOA classification scheme can be used to better identify which aspects of SOA they are targeting:

  1. SOA is Dead, long live services! This was the title of a blog posting by Anne Thomas Manes, VP and Sr. Analyst at Burton Group. This post clearly indicates one of the key problems caused by a narrative definition of SOA. Using the classification scheme, an effective and positive statement on SOA could be that businesses are being successful with Services Design and System Design classes.
  2. Dealing with the concept of SOA failure. Instead of businesses failing at SOA, organizations can use the classification scheme to better target their SOA initiatives. For example, the business can target System and Semantic Design class initiatives because they are more pragmatic and require less up front investment, whereas Enterprise SOA Design requires large up-front investment and provides relatively little perceivable value without continued investment.
  3. SOA as a means of enabling better IT/business communications. Unless companies target Semantic Design class efforts, they will most likely not reach this target goal. Companies focused on System Design and Enterprise SOA Design class initiatives will gain benefit from reducing dependencies between entities, but the net gain of these changes will not be recognized by the business.

Classifications Are Not Silos

The classes defined in this scheme are not designed to create silos since silos force mutual exception. Indeed, there are good examples where these classes overlap. The following is just one example of Application and Service Design classes overlapping.

REST-based Web Services is an aspect of the Application Design class that overlaps with the Service Design class. REST-based Web Services treat the Web as a pool of informational resources each uniquely represented by their own moniker called a Uniform Resource Locator (URL). The concept that a REST endpoint produces machine-readable representations of the information at that URL is an aspect of the Application Design class. The concept that a REST endpoint produces human-readable rendering of the information at that URL is an aspect of the Service Design class. Hence, as accurately stated by many, the Web is categorically SOA.


SOA is still a relatively new creation as far as architectural methodologies and design patterns. Still, the lack of coherence and clarity surrounding SOA has acted to inject confusion and mismanaged expectations regarding the benefits it can provide. Its rapid ascent in the business community, which was directed at management, did little to allow it to mature before being presented up as the saving grace of IT; and, now that it has been raised up on a pedestal, it is poised to become IT's next sacrificial lamb.

SOA practitioners have had to consistently defend themselves from attacks on their work as pundits, analysts, consultants and other practitioners shoot SOA idioms over the bow in the form of articles, blog postings and Twits. Hopefully, breaking the big SOA beast into smaller digestible pieces as I have done here with this SOA Classification Scheme will minimize the impact of outside influences since it allows the expected benefits of SOA to be more easily identified and scoped.

More Stories By JP Morgenthal

JP Morgenthal is a veteran IT solutions executive and Distinguished Engineer with CSC. He has been delivering IT services to business leaders for the past 30 years and is a recognized thought-leader in applying emerging technology for business growth and innovation. JP's strengths center around transformation and modernization leveraging next generation platforms and technologies. He has held technical executive roles in multiple businesses including: CTO, Chief Architect and Founder/CEO. Areas of expertise for JP include strategy, architecture, application development, infrastructure and operations, cloud computing, DevOps, and integration. JP is a published author with four trade publications with his most recent being “Cloud Computing: Assessing the Risks”. JP holds both a Masters and Bachelors of Science in Computer Science from Hofstra University.

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