A universal format for data on the Web. Using a simple relational model, it allows structured and semi-structured data to be mixed, exported and shared accross different applications. RDF data describe all sorts of things, and where XML schemas just describe documents, RDF and OWL schemas ("ontologies") talk about the actual things. This gives greater re-use. where XML provides interoperability within one application (e.g. bank statements) using a given schema, RDF provdies interoperability across applications (eg import your bank statements into your calendar).

RDF started as framework for metadata; providing interoperability between applications that exchange machine-understandable information on the Web. RDF emphasizes facilities to enable automated processing of Web resources and as such provides the basic building blocks for supporting the Semantic Web. RDF metadata can be used in a variety of application areas; for example: in resource discovery to provide better search engine capabilities; in cataloging for describing the content and content relationships available at a particular Web site, page, or digital library; by intelligent software agents to facilitate knowledge sharing and exchange; in content rating; in describing collections of pages that represent a single logical "document"; for describing intellectual property rights of Web pages, and in many others. RDF with digital signatures will be key to building the "Web of Trust" for electronic commerce, collaboration, and other applications.