Most of the information about RDF is not in the FAQ but is linked from
There are is also more Frequently Asked Questions supported by the RDF interest group as a commuity.
RDF--the Resource Description Framework--is 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.
RDF provides the following features:
Further development will enable RDF to also provide:
In general, RDF provides the basis for generic tools for authoring, manipulating, and searching machine understandable data on the Web thereby promoting the transformation of the Web into a machine-processable repository of information.
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:dc="http://purl.org/dc/elements/1.1/">
<rdf:Description rdf:about="http://doc"
dc:creator="Joe Smith"
dc:title="My document"
dc:description="Joe's ramblings about his summer vacation."
dc:date="1999-09-10" />
</rdf:RDF>
Note: that this technique creates a mixed-format document which cannot (as of August 2003) be validated as HTML. The RDFCore Working Group consequently encourage metadata to be linked from rather than embedded in your HTML documents. See the RDF Core issue resolution on this topic for details. The public-rdf-in-xhtml-tf mailing list has been established to investigate strategies for embedding RDF that support HTML validation.
For http://doc substitute the Web address of the document
itself. If you don't know the Web address or if it may change, or if the
document has multiple Web addresses, you can use the empty string ("").
For Joe Smith, substitute the name of the person or
organization primarily responsible for creating the intellectual content of
the page.
Do not change the URIs in the two xmlns: attributes; those URIs are what tell others exactly what this tiny bit of XML really means!
For further reading on the Dublin Core elements, see "Dublin Core Metadata Element Set: Reference Description". The Dublin Core Metadata Initiative (DCMI) is working on a more sophisticated representation of qualified Dublin Core metadata. See the DCMI Architecture pages for information about the status of this work.
There are many tools and applications and no one list can do justice to them. However, the DAML website has a large list of tools. (DAML is the name for the US Government's sponsored project to help develop the Semantic Web RDF) They include commercial software, free software and research projects. They include stores, query systems, inference engines, reformatters, report generators, data converters, and so on. The RDF Interest Group is a good place to ask for something you can't find.
RDF is a collaborative design effort; no one individual or organization invented RDF. Several W3C Member organizations contribute intellectual resources to its development.
While RDF started as an extension of the PICS content description technology, it also draws upon the XML design as well as technology submissions by Microsoft (XML Web Collections) and Netscape (XML/MCF). Other documents, such as Microsoft's XML-Data paper, Site Map proposals, and the Dublin Core/Warwick Framework have also influenced the RDF design. (See OCLC's Nov'97 Press Release.)
PICS-1.1 is a W3C Recommendation that predates RDF. One of the requirements for the RDF design was that it be able to express everything that a PICS-1.1 label can express, and that it be possible to automatically translate PICS-1.1 labels into RDF format without loss of information. Any future technical work on PICS will evolve it to using RDF. The W3C PICS Interest Group is chartered to decide when this transition is appropriate. Software and Web content using PICS-1.1 will remain a supported W3C recommendation for as long as the market demands. Our current expectation is that PICS-1.1 and an equivalent expression of PICS ratings in RDF will both be useful for quite some time. See more recent note.
They were not widely deployed nor used in the form specified in the 1998 recommendation. The RDF Core Working Group examined the implementation experience available and decided to remove it. See Issue rdfms-abouteachprefix: Something should be done about aboutEachPrefix construct. More recent work suggests refactoring it into a general-purpose URI-level-breaking property (log:uri among the cwm built-ins) along with string utilities, along with rules and/or ontology-level axioms. For example, see public-groups-filter.n3.
See also BreakingURIOpacity in the ESW Wiki for more details and discussion