RDF and Traditional Query Architectures

The Resource Description Framework (RDF) is a step towards the support for integrated and uniform access to information sources. It is designed to standardize the definition and use of metadata descriptions of Web-based resources. It is complemented with RDF Schema (RDFS) that lets developers define an extensible, object-oriented type system for RDF data models. While RDF is targeted towards representing metadata, it can represent the underlying data as well. Together, RDF and RDFS provide a sound basis for the capture of domain knowledge in a form that lends itself for automatic processing. Since the Web is inherently distributed, RDF querying systems should also be able to handle the distribution of multiple, autonomous RDF repositories. A sound approach is needed for querying distributed RDF sources to disclose the information they contain. In this chapter we examine several architectures for querying distributed RDF (meta)data and point out a number of issues that will have to be dealt with in order to provide a viable solution. The discussion traces the development of distributed applications that attempt to exploit the promises of interoperability of the Semantic Web and have to deal with the requirements that arise from that. The chapter focuses on the problems associated with the introduction of RDF (meta)data in the distributed information system arena.