Programming WCF Services, 3rd Edition

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 such details. 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. This tenet is the modern incarnation of the old object-oriented adage that the application should maximize encapsulation and information hiding.

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, enabling it to evolve separately from them. ...