The Semantic Web: The OWL has landed

Web Ontology Language (OWL), a key to the future of the Semantic Web envisioned by W3C director Tim Berners-Lee, is ready for implementation.

OWL received Candidate Recommendation status from the W3C this month, which, according to the XML standards body, means it is "stable and appropriate for implementation."

The language provides a standard way to define Web-based ontologies so that data can be described as what it is -- an enzyme in a biological application or a hotel in a travel industry application -- instead of as document in a tree structure or other database abstraction.

As an example of an implementation, the W3C points to the Travel Agent Game developed by a group at Agentcities (, a global, collaborative effort to construct an open network of online systems hosting diverse, agent-based Web services. Agentcities is using travel.owl with an ontology that includes terms such as travel customers, intineraries and reservations.

Other early adopters include bioinformatics and medical applications, such as BioPax (, a Web site for researchers seeking to exchange biological information using ontologies. BioPax is standardizing on XML Schema and OWL.

While ontologies are not new, especially in the scientific community, the purpose of OWL is to provide a standardized format that is compatible with the architecture of the World Wide Web and the Semantic Web, according to the W3C announcement.

The standarization of ontologies in the OWL langauge will make data on the Web "more machine processable and reusable across applications," according to Berners-Lee. As he has explained it in the past, the Semantic Web using XML-based ontologies rather than traditional tree structures will make it easier for Web services applications to process data from multiple sources.

About the Author

Rich Seeley is Web Editor for Campus Technology.