SOA basics

Numerous vendors, application providers, system integrators, architects, authors, analysts firms, and standards bodies provide definitions of SOA. The definitions of SOA are diverse. Most are complementary and do not conflict with each other. SOA has a variety of definitions because the definition is often tuned to a specific audience, as explaining SOA to a CEO is different from explaining SOA to a programmer. The term service orientation is often used synonymously with SOA, but just like SOA it has a wide range of interpretations. Service orientation is broader and represents a way of thinking about services in the context of business and IT. This book makes no distinction between SOA and service orientation and in some cases may use the two terms synonymously.

An agreed-upon definition for SOA eludes the industry. Anyone reading Wikipedia’s definition page for SOA will see the challenges of trying to gain consensus on an SOA definition. Standards bodies, the OASIS group, and the Open Group have provided complementary but different SOA definitions. Presented with a blank sheet of paper, an artist sees a canvas. A poet might fill it with verse. An engineer seizes the opportunity to make a paper plane. Kids may see it as a future pile of spit wads. SOA is that blank sheet of paper.

To the chief information officer (CIO), SOA is a journey that promises to reduce the lifetime cost of the application portfolio, maximize return on investment (ROI) in both application and technology resources, and reduce lead times in delivering solutions to the business.

To the business executive, SOA is a set of services that can be exposed to their customers, partners, and other parts of the organization. Business capabilities, function, and business logic can be combined and recombined to serve the needs of the business now and tomorrow. Applications serve the business because they are composed of services that can be quickly modified or redeployed in new business contexts, allowing the business to quickly respond to changing customer needs, business opportunities, and market conditions.