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W3C Issues OWL as Candidate Recommendation

The World Wide Web Consortium (W3C) Tuesday issued Web Ontology Language (OWL) as a W3C Candidate Recommendation, paving the way for making data on the Web more machine processable and providing a stepping stone in the direction of the W3C's vision for the Semantic Web.

The W3C said OWL (the working group disliked the more accurate 'WOL' acronym) is a language for defining structured, Web-based ontologies which can enable richer integration and interoperability of data across application boundaries. With OWL, the W3C hopes to make it possible for information contained in documents to actually be processed by applications, rather than just presented to humans.

According to the OWL Requirements Document: "An ontology defines the terms used to describe and represent an area of knowledge. Ontologies are used by people, databases and applications that need to share domain information (a domain is just a specific subject area or area of knowledge, like medicine, tool manufacturing, real estate, automobile repair, financial management, etc.). Ontologies include computer-usable definitions of basic concepts in the domain and the relationship among them...They encode knowledge in a domain and also knowledge that spans domains. In this way, they make that knowledge reusable."

So what can OWL be used for? The OWL Working Group identified six main areas:
  • Web portals, where it can be used to create categorization rules to enhance search
  • Multimedia collections, where it can be used to enable content-based searches for non-text media
  • Corporate Web site management, where it can be used for automated taxonomical organization of data and documents, as well as mapping between corporate sectors
  • Design documentation, where it can be used for explication of 'derived' assemblies (like the wing span of an aircraft) and the explicit management of constraints
  • Intelligent agents, where it can be used for expressing user preferences and/or interests, as well as content mapping between Web sites
  • Web services and ubiquitous computing, where it can be used for Web service discovery and composition as well as rights management and access control.

"OWL is an important step for making data on the Web more machine processable and reusable across applications," said Tim Berners-Lee, director of the W3C. "We're encouraged to see OWL already being used as an open standard for deploying large scale ontologies on the Web."

OWL has its roots in two research efforts: a draft language known as the DARPA Agent Markup Language Ontology notations (DAML-ONT) and Ontology Interface Layer (OIL), the latter of which was developed by European researchers with the support of the European Commission. DAML and OIL were brought together through an ad hoc group of researches called the Joint US/EU committee on Agent Markup Languages.

OWL builds on that work in an effort to further the W3C's vision of the Semantic Web.

"The Semantic Web is a vision for the future of the Web in which information is given explicit meaning, making it easier for machines to automatically process and integrate information available on the Web," the W3C said.

To make the Semantic Web happen, the W3C said computers have to be able to access structured collections of information and sets of inference rules so that they can use the information to conduct automated reasoning. OWL extends the Resource Description Framework schema to allow for the expression of complex relationships between different RDFS classes, and also adds additional vocabulary for describing properties and classes.