Key Features of an SOA

The following section outlines some of the key technology features that must be present in a true service-oriented architecture implementation.

• Loose coupling. This ensures that services and the systems that use them do not need to be on the same operating platform or share the same language in order to interface. This flexibility allows services to remain useful even once the technology that created it has become obsolete.
• Well-defined interfaces. The service interface must be designed in a language-neutral format (typically XML). The neutral interface assists with the loose-coupling discussed above, removing the need for services and the system that requests them to be programmed in the same language.
• Independent service design. Services in an SOA should be built using independent, self-contained requests – which do not require information to be passed between one request and another. Services must also be independent of the context of other services. This ensures that each service is treated by external entities as a stand-alone unit.
• Service granularity. Services should have a small number of operations and relatively large, complex messages. This practice makes sure that only the fewest calls necessary are made in order to use the service.
• Neutral message structure. Messages should be sent in a format that is not specific to any one platform. This feature goes along with the language-neutral requirement for the interface between services. Once again, a platform-neutral message structure is typically achieved using XML.
• Network oriented. Given the interconnectivity between operations in a modern enterprise, services are usually geared towards being used over a network. This is why many IT experts refer to Web services as an SOA element. While services do not necessarily have to be Web oriented, most modern implementations are designed to work over a network.