Service Granularity in SAP

Question

I wants to know if SAP banking supports Service Granularity.
Are the services Fine grained or Course grained.
Please provide a pointer or document abt SOA and web services for SAP / SAP banking.

Answer 1

Hi
I picked this up, hope this is of some help.
Service Granularity Challenge with SAP's ESA
SAP uses its Netweaver based development infrastructure to define services in a SOA.
The business services are defined in Netweaver Developer Studio (NWDS) which is also known as the CAF (Composite Application Framework) Core. They have three main constructs namely an external service, an entity service and an application service.
An external service allows for the linkage to services defined outside the CAF Core environment sandbox.
An entity service essentially models an operation on a business object (BO) as a service. Typically these map to existing BAPI's that work on business objects that are stored in the SAP Business Warehouse (BW). Operations on business objects being used as a basis to define services, to me, is a very parochial approach to service definition and often becomes too fine grained to follow the footsteps of a service-proliferation-syndrome.
Application Services are defined as coarser-grained services that combine or use multiple entity services with some applied business logic to tie them together. Even here, it is more of a bottom up approach to service definition. I fear that, using this approach, we are missing the key issue of aligning services to business processes. The concept of business aligned services seems to be lost in the mechanism, somewhere !!!
There is another tool, more of a somewhere-inbetween-a design-and-a-runtime mechanism to define orchestrations of services, based on the SAP Guided Procedures (GP). GP has concepts of actions, blocks and callable objects. Actions and blocks can be simulated as a composition of services together - ala service composition. But then, these service composites, are not pushed down to the business service layer - which to me is an issue.
The Enterprise Services which SAP defines are done in an altogether differnt way. There the services are conceptualized from a business point of view only and defined and orchestred in SAP Exchange Infrastructure, while implementing proxy remains in the backend business system like ERP, CRM, etc. These Enterprise Services represents a well-defined business functionality only.
The services that are defined in CAF Core are rather composite services which are predominantly based on the Enterprise Services. Though at present we use BAPI (which are rather technical API for business objects) to define the dependency of the entity service with the existing assests, but in future these will be replaced by Enterprise Services as day by day more and more Enterprise Services are getting published by SAP and added to the UDDI service registry. So in that sense we can define entity and external services based on the Enterprise Services only and in the Application Service we can model the business logic of the composite application, which in turn becomes a composite service.
Rgds
suresh