W3C’s OWL language has just advanced to ‘Candidate Recommendation’ stage. OWL is used to publish and share sets of terms called ontologies; FOAF is one such ontology, as it uses OWL to define its terms in a machine-processable way.
The FOAF project relies on a number of W3C standards, including XML, RDF and the Web Ontology language, OWL. As OWL stabilises, we should benefit from an increasing number of tools that exploit the ability to reason about OWL-based vocabularies such as FOAF.
FOAF makes use of OWL in particular for describing when a certain kind of property (eg. ‘homepage’, ‘mbox’, ‘dnaChecksum’, ‘mbox_sha1sum’, ‘jabberID’ etc.) is uniquely identifying. This mechanism underpins the working of many FOAF aggregators and toolkits. FOAF benefits from W3C’s work on OWL, since it allows us to adopt standard conventions shared across the Semantic Web community, rather than invent conventions that would only be understood by FOAF tools. Consequently FOAF implementations can make more use of generic RDF-based software, allowing FOAF developers to concentrate on FOAF-related functionality rather than on basic data-merging and storage techniques. This is particularly important to us as FOAF is designed to be freely mixed with other Semantic Web data (eg. geographic, calendar, taxonomy, bibliographic etc.).
See the W3C news item, press release and FAQ for more information on OWL and its relationship to other W3C technologies.