Approaches
As you learned in Chapter 3, Service Identification and Design, there are different approaches you can take to realize an SOA.
When you design a service top-down, you start by analyzing the need for certain operations from the perspective of the consumers of the service. There are two types of consumers relevant in this case: the processes and the user interface. Sometimes multiple processes and interfaces use the same service; other services are specific to one process or user interface component. These services then can be designed: we design the service interface, a contract and build it from scratch. This approach works well for green field situations, when a service or the type of data needed by the processes and the user interface do not exist yet.
Example – Document Management Service
Take for example a company that does not have a Document Management System yet. In that situation it makes sense to identify the document service operation and messages based on the requirements...
