Resource Description Framework (RDF)

The Resource Description Framework (RDF) is a general framework for how to describe any Internet resource such as a Web site and its content. An RDF description (such descriptions are often referred to as metadata, or "data about data") can include the authors of the resource, date of creation or updating, the organization of the pages on a site (the sitemap), information that describes content in terms of audience or content rating, key words for search engine data collection, subject categories, and so forth. The Resource Description Framework will make it possible for everyone to share Web site and other descriptions more easily and for software developers to build products that can use the metadata to provide better search engines and directories, to act as intelligent agents, and to give Web users more control of what they're viewing. The RDF is an application of another technology, the Extensible Markup Language (XML), and is being developed under the auspices of the World Wide Consortium (W3C).

A certain amount of metadata is already provided for Web site resources using the Hypertext Markup Language (HTML). For example, when we wrote this page, we added HTML statements containing key words that describe the content of this definition and that are used by search engines for indexing. We also added a one-sentence description that can be shown by search engines. (These statements, called META tag statements, are invisible to you unless you click on this page and then right-click on "View source"). Less formally, the "Created on" or "Updated on" date at the bottom of this definition is also metadata - that is, data that tells you something about the data or content on this page. These are simply a few examples of many possible existing and future resource descriptions needed about a Web resource.

Originally conceived as an extension of the content rating PICS Recommendation, the RDF will in time subsume it, with the idea that it can express any data that a PICS-1.1 label can express. However, both RDF and the equivalent PICS expression are expected to be in use for a while.


Here are some of the likely benefits:

  • By providing a consistent framework, RDF will encourage the providing of metadata about Internet resources.
  • Because RDF will include a standard syntax for describing and querying data, software that exploits metadata will be easier and faster to produce.
  • The standard syntax and query capability will allow applications to exchange information more easily.
  • Searchers will get more precise results from searching, based on metadata rather than on indexes derived from full text gathering.
  • Intelligent software agents will have more precise data to work with.

How RDF Works

An Internet resource is defined as any resource with a Uniform Resource Identifier (URI). This includes the Uniform Resource Locators (URL) that identify entire Web sites as well as specific Web pages. As with today's HTML META tags, the RDF description statements, encased as part of an Extensible Markup Language (XML) section, could be included within a Web page (that is, a Hypertext Markup Language - HTML - file) or could be in separate files.

RDF is now a formal W3C Recommendation, meaning that it is ready for general use. Currently, a second W3C recommendation, still at the Proposal stage, proposes a system in which the descriptions related to a particular purpose (for example, all descriptions related to security and privacy) would constitute a class of such like descriptions (using class here much as it is used in object-oriented programming data modeling and programming). Such classes could fit into a schema or hierarchy of classes, with subclasses of a class able to inherit the descriptions of the entire class. The schema of classes proposal would save having to repeat descriptions since a single reference to the class of which a particular RDF description was a part would suffice. The scheme or description of the collection of classes could itself be written in RDF language.

Contributor(s): Irene Driessen and Simon Smith
This was last updated in September 2005
Posted by: Margaret Rouse

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