Service-Oriented Architecture Governance for the Services Driven Enterprise

6.10. DECOUPLING POLICIES FROM SERVICES

In order to truly achieve the loose coupling goals of SOA, we must make greater progress toward decoupling SOA policies from services. Achieving this requires much more effort in the area of SOA policies, services design operations, SOA infrastructure and runtime platforms, and the overall process of design through runtime governance. The realization of loose coupling of Web services, for example, has been limited by immaturity of Web services and SOA standards and by lack of understanding of SOA governance and policy enforcement in general.

From a technical perspective, the lack and relative immaturity of standards around SOA policies has been a primary factor in the failure to achieve loose coupling of services. While simple service implementations have been able to achieve some degree of loose coupling, more complex scenarios involving security, reliability, routing, versioning, and service behavior are more challenging. It is in this domain that immaturity of standards has caused developers to hard code these policy requirements into service implementations and thereby create brittleness and service dependencies.^[]

^[] Toufic Boubez, Layer 7 Technologies: "Enabling SOA Runtime Policy," 2006, p. 4.

Another area of discussion involves whether policy assertions should be contained in the WSDL document or hard coded in the service. There has been recent discussion of the need to decouple policies from service descriptions because it is likely ...