There has been some confusion around the mechanism and methodology to create Enterprise Services vis-a-vis the development of Composite Applications in SAP.
The identification, development and certification of enterprise services follow a strict internal governance mechanism inside SAP. Enterprise Services are proposed either by the business application suite groups (e.g. SCM, SRM, CRM) inside SAP or by a member of the SAP IVN (Industry Value Network). Enterprise Service definition is a top-down approach, one in which a service is defined in relevance to a business functionality that it tries to solve. It has the much needed business alignment that business-level services ought to provide. Enterprise Services are defined in SAP XI. The message structure are defined first. The message interface is defined by using the definitions of the message structures. A message interface is exposed as a service which is then developed using NWDS and XI and then provisioned into the Enterprise Service Repository (ESR).
Composite applications on the other hand are developed more or less based on a bottom up approach. A composite is created using the CAF-Core and CAF-GP tools of the Netweaver platform. The UI elements are developed either in WebDynPro or Visual Composer. The CAF-Core uses services that are either defined in the ESR or it can create services based on the various back-end systems e.g. CRM, ERP which expose their IT functionality through BAPI's. CAF-Core defines two types of services: Entity Services (encapsulate the business objects from the back-end system) and Application Services (which combine entity services, add business logic on top of them and are exposed to be consumed by the elements of CAF-GP, WebDynPro and Visual Composer). CAF-GP is a mechanism to simulate the creation of business processes through the use of constructs like Actions, Blocks, Processes and Callable Objects. The Callable Objects are used to invoke the Application Services in CAF-Core. Processes at the CAF-GP are subsequently deployed and invoked through the SAP Netweaver Portal.
Hence, there is an essential difference in methodology in SAP between defining and developing Enterprise Services and developing Composite Applications.
I would be really interested to see some more light shed on this topic.