The Semantic Web is a vision of the future of the World Wide Web. Tim Berners-Lee advocates it, but the semantic web builds on many older hypertext systems back to the late 1960s, and lately the convergence of text-and-markup with knowledge representation.
A "semantic" web is one consisting of documents that are put together in such a way that it facilitates automated information gathering and research in a far more meaningful way than can be accomplished with current web search tools. The most basic element is the semantic link <-- see that article for details.
The usability and usefulness of the Web and its interconnected resources will be enhanced through:
- documents 'marked up' with semantic information (an extension of the <meta> tags used in today's Web pages to supply information for Web search engines using web crawlers). This could be machine-readable information about the human-readable content of the document (such as the creator, title, description, etc of the document) or it could be purely metadata representing a set of facts (such as resources and services elsewhere in the site).
(Note that anything that can be identified with a Universal Resource Identifier (URI) can be described, so the semantic web can reason about people, places, ideas, cats etc.)
- common metadata vocabularies (ontologies) and maps between vocabularies that allow document creators to know how to mark up their documents so that agents can use the information in the supplied metadata (so that Author in the sense of 'the Author of the page' won't be confused with Author in the sense of a book that is the subject of a book review).
- automated agents to perform tasks for users of the Semantic Web using this metadata
- web-based services (often with agents of their own) to supply information specifically to agents (for example, a Trust service that an agent could ask if some online store has a history of poor service or spamming).
All current web technologies are likely to have a role in the semantic web (in the sense of semantic world wide web), for instance :
- DOM The Document Object Model which provides a set of standard interfaces for accessing XML and HTML document components.
- XPath, Xlink, XPointer
- XInclude XML fragment XML query language XHTML
- XML Schema, RDF (Resource Description Framework)
- XSL, XSLT Extensible Stylesheet Language
- SVG (Scalable Vector Graphic)
- the concept of metadata.
- Topic maps
- Dublin Core
- Knowledge representation
- Knowledge technologies
- Web syndication - RSS and Atom/Echo