RDF

Resource Description Framework (RDF) is a foundation for processing metadata in order to provide interoperability between applications that exchange machine-understandable information on the Web. The World Wide Web was originally built for human consumption, and although everything on it is  machine-readable, this data is not  machine-understandable.  By describing the data contained on the Web as  metadata, we can move toward enabling automated processing of Web resources. 

Note: Metadata is "data about data" (for example, a library catalog is metadata, since it describes publications) or specifically in the context of this specification "data describing Web resources". The distinction between "data" and "metadata" is not an absolute one; it is a distinction created primarily by a particular application, and many times the same resource will be interpreted in both ways simultaneously.

RDF 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 for expressing the  privacy preferences of a user as well as the  privacy policies of a Web site. RDF with  digital signatures will be key to building the "Web of Trust" for electronic commerce, collaboration, and other applications.

The syntax of RDF uses the Extensible Markup Language [XML]: one of the goals of RDF is to make it possible to specify semantics for data based on XML in a standardized, interoperable manner. RDF and XML are complementary: RDF is a model of metadata and only addresses by reference many of the encoding issues that transportation and file storage require (such as internationalization, character sets, etc.). For these issues, RDF relies on the support of XML. It is also important to understand that this XML syntax is only one possible syntax for RDF and that alternate ways to represent the same RDF data model may emerge.