Programming WCF Services

Tenets and Principles

The service-oriented methodology governs what happens in the space between services (see Figure A-1). There is a small set of principles and best practices for building service-oriented applications referred to as the tenets of service-oriented architecture:

Service boundaries are explicit

Any service is always confined behind boundaries such as technology and location. The service should not make the nature of these boundaries known to its clients by exposing contracts and data types that betray its technology or location. Adhering to this tenet will make aspects such as location and technology irrelevant. A different way of thinking about this tenet is that the more the client knows about the implementation of the service, the more the client is coupled to the service. To minimize the potential for coupling, the service has to explicitly expose functionality, and only operations (or data contracts) that are explicitly exposed will be shared with the client. Everything else is encapsulated. Service-oriented technologies should adopt an “opt-out by default” programming model, and expose only those things explicitly opted-in.

Services are autonomous

A service should need nothing from its clients or other services. The service should be operated and versioned independently from the clients. This will enable the service to evolve separately from the client. The service is also secured independently and it protects itself and the messages sent to it regardless ...