Why layer a service?
An important aspect of SOA design is that service boundaries should be explicit, which means hiding all the details of the implementation behind the service boundary. This includes revealing or dictating what particular technology was used.
Furthermore, inside the implementation of a service, the code responsible for the data manipulation should be separated from the code responsible for the business logic. So in the real world, it is always good practice to implement a WCF service in three or more layers. The three layers are the service interface layer, the business logic layer, and the data access layer.
Service interface layer: This layer will include the service contracts and operation contracts that are used to define the service interfaces that will be exposed at the service boundary. Data contracts are also defined to pass in and out of the service. If any exception is expected to be thrown outside of the service, then Fault contracts will also be defined at this...
