Enterprise SOA

What are two ways to create services in ABAP?

When creating services in ABAP, there are essentially two ways to approach the problem. You can start at the back end, with an existing application, and say, "I want to service enable that particular piece of functionality." This approach quickly gets some services that you need up and running. In SAP parlance, this approach is called creating services from the inside out because we start with the implementation and move out toward the interface.

Creating services from the outside in is the opposite approach; you start with the interface and work in toward the implementation. While creating services from the inside out entails starting with a piece of application functionality, creating services from the outside in asks you to start with modeling. Creating services from the outside in, starting with modeling, is the preferred—one might say the ultimate—approach to creating enterprise services. The process as it stands at this writing involves modeling data types; at the end of this chapter, we'll look at the direction this process will take in upcoming releases of SAP NetWeaver, where modeling becomes more important and entails working with business objects, as discussed in Chapter 5.

Obviously, creating services from the inside out and the outside in starts from different places; the semantics of the terms imply as much. But they also differ in other important ways. Services created from the inside out follow the message response pattern, ...