The RDF Data Access Working Group has published the fourth public working draft of RDF Data Access Use Cases and Requirements. According to the introduction,
The W3C's Semantic Web Activity is based on RDF's flexibility as a means of representing data. While there are several standards covering RDF itself, there has not yet been any work done to create standards for querying or accessing RDF data. There is no formal, publicly standardized language for querying RDF information. Likewise, there is no formal, publicly standardized data access protocol for interacting with remote or local RDF storage servers.
Despite the lack of standards, developers in commercial and in open source projects have created many query languages for RDF data. But these languages lack both a common syntax and a common semantics. In fact, the extant query languages cover a significant semantic range: from declarative, SQL-like languages, to path languages, to rule or production-like systems. The existing languages also exhibit a range of extensibility features and built-in capabilities, including inferencing and distributed query.
Further, there may be as many different methods of accessing remote RDF storage servers as there are distinct RDF storage server projects. Even where the basic access protocol is standardized in some sense—HTTP, SOAP, or XML-RPC—there is little common ground upon which to develop generic client support to access a wide variety of such servers.
The following use cases characterize some of the most important and most common motivations behind the development of existing RDF query languages and access protocols. The use cases, in turn, inform decisions about requirements, that is, the critical features that a standard RDF query language and data access protocol require, as well as design objectives that aren't on the critical path.
Use cases include: