Semantic Web

What it is

The Semantic Web is a standards-based approach to describing data on the Web so that its meaning can be shared and reused. The World Wide Web Consortium (W3C) describes RDF and OWL as Semantic Web standards that provide a framework for asset management, enterprise integration, and the sharing and reuse of data on the Web.^[1] The aim is not merely to publish documents but to publish descriptions that different systems can use.

How it works

The standards are intended to span application, enterprise and community boundaries. W3C says these standard formats for data sharing let users who do not share the same software share the same information.^[1] A useful contrast is with XML: XML provides rules and syntax for structured documents, but it imposes no semantic constraints on what those documents mean; RDF supplies a clear set of rules for simple descriptive information.^[1] In practice, a shared description can act as a common layer: one application can publish information in a standard form, and another application, even one built with different software, can reuse that information because both sides follow the same description rules.^[1] OWL is the other standard W3C names alongside RDF in this framework.^[1]

Where it came from

The Semantic Web Activity builds on other W3C Activities, such as XML, and focuses on standard technologies on top of XML that support the growth of the Semantic Web.^[1] The WebOnt Working Group page records that the group started on 1 November 2001, and that OWL became a W3C Recommendation on 10 February 2004.^[2] W3C says deployment of these standards in commercial products and services signalled the transition of Semantic Web technology from a largely research and advanced-development project over the preceding five years to practical technology in mass-market tools.^[1] That transition matters because it marks the point at which the standards were no longer only an experimental research topic.

Where it is used

W3C lists content creation applications, Web site management tools, enterprise application integration and cross-application data reuse among the uses of RDF and OWL.^[1] These uses follow from the same promise: standard descriptions can cross application, enterprise and community boundaries, so information can be shared even when the software differs.^[1] Within an enterprise, integration work can use the standards to connect systems; across applications, data can be reused rather than copied into separate silos. The standards are therefore presented as a framework for asset management and for sharing data on the Web, not only for publishing pages.^[1]

Limits

The standards do not make meaning automatic. XML alone provides syntax without semantic constraints, so the descriptive layer has to come from RDF and OWL and from shared agreement on what the descriptions mean.^[1] The commercial deployment W3C describes was a milestone, not an end point; it showed that the technology could appear in mass-market tools.^[1] The framework is broad—asset management, enterprise integration, content creation, site management and cross-application reuse—so its value depends on common formats being used across the boundaries it is meant to bridge.^[1]