SOA - Service Orientation Applied

SOA and Web services are not the same

The industry has witnessed enough hype on SOA. A common source of confusion in architects mind is whether Web services are same as SOA?

While web services have evolved as a technology for distributed computing based on standardization of different imperatives involved in inter application communications (e.g. standard

for data, standard for messages being exchanged, standard for describing of the application functionality etc.). Thus Web services based on these core set of standards including XML Schema, SOAP, WSDL are merely yet another mechanism for distributed applications to communicate. It is vital to understand this.

SOA on the other hand is an architectural paradigm which is based on a set of principles for any software functionality provider to interact with potential users of the software. In particular SOA principles advocate a loosely coupled mechanism for software providers to interact with other requestors via a strict contract which is indendepent of the requestor. Given this kind of goal of SOA, a key question is whether SOA is realizable only by Web services?

Key thing to understand is Web services do bring a high level of standardization and the interoperability thereupon to enable different providers to interact, however it is not necessary to use Web services to achieve SOA always. e.g. in a pure J2EE environment a Web service would be an overkill.

Likewise it is possible to use Web services not necessarily in a SOA based design, by using tight coupling as in RPC kind of invocations. Hence it is possible to do Web services without SOA principles.

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