Can I reuse objects such as data types and message types that are shipped by SAP?
Yes. All the content shipped by SAP (including modeling objects such as business objects, Process Components, and ES Repository objects, such as Data types and Message Types) can reused to model services in the ES Repository. As a matter of fact, SAP encourages the reuse of the Global Data types, the fundamental building blocks of services provided by SAP that is delivered as part of ES Repository, to standardize services.