OWL

Draft

Definition

• The OWL Web Ontology Language is intended to be used when the information contained in documents needs to be processed by applications, as opposed to situations where the content only needs to be presented to humans.

• OWL is an XML application, i.e. a vocabulary extension of RDF and it is seen as major element of the semantic web framework.

• “The OWL Web Ontology Language is designed for use by applications that need to process the content of information instead of just presenting information to humans. OWL facilitates greater machine interpretability of Web content than that supported by XML, RDF, and RDF Schema (RDF-S) by providing additional vocabulary along with a formal semantics. Full” (OWL Web Ontology Language Overview, retrieved 14:18, 23 November 2006 (MET))

Sublanguages

OWL has three increasingly-expressive sublanguages: OWL Lite, OWL DL, and OWL. According to [Wikipedia],

• OWL Lite allows to define a classification hierarchy and simple constraints.

• OWL DL allows maximum expressiveness while retaining computational completeness (all conclusions are guaranteed to be computed) and decidability (all computations will finish in finite time). In other words, OWL DL includes all OWL language constructs, but they can be used only under certain restrictions. OWL DL is related to Wikipedia:description logic.

• OWL Full is meant for users who want maximum expressiveness and the syntactic freedom of RDF with no computational guarantees.

Software

(not tested for real so far by DSchneider)

• ConceptVISTA, An OWL-based formalization of the [[DualPlus Toolkit | DualPLUS learning activities taxonomy], but it also can be used for other ontologies.

• Model Futures OWL Editor (WinXP, Beta, Freeware on 14:18, 23 November 2006 (MET))

• SWOOP, A Hypermedia-based Featherweight OWL Ontology Editor. It is meant for rapid and easy browsing and development of OWL ontologie. (Freeware)

• Protégé-Owl. Freeware, registration required.

OWL in education

Here is a hypothetical example provided by Clark et al. (2004).

To see how OWL can be used, we return to our earlier example. Suppose the C.P. Snow Society wants to organize its bibliographic information already encoded in RDF. To take a simple example, they would like to distinguish between works by Snow and works about him. In OWL, we can express these concepts using class expressions, in particular, restrictions on the various properties a work has. For example, the class of work by C.P. Snow is just the set of work which have http://www.cpsnow.org/cpsnow (the person designated by this URI) as their dc:author, while the class of works by C.P. Snow is just the set of works which have http://www.cpsnow.org/cpsnow as (one of) their dc:subject(s). We can easily express these definitions in OWL, give names to these concepts (e.g., http://www.cpsnow.org/ WorksByCPSnow and http://www.cpsnow.org/ WorksAboutCPSnow and expect an OWL system to correctly infer which works we've already described fall into which class. The C.P. Snow society can build upon these concepts to express the distinction between works and articles solely written by Snow and collaborative works (e.g., by defining WorksByOnlySnow as a subclass of WorksByCPSnow where there is only one author, and CollaborationsWithSnow as the subclass of WorksByCPSnow where there is at least one author who isn't snow).

While helpful for organizing the C.P. Snow society's Web site, such an ontology only becomes interesting, and only become a true Web ontology, when it is published on the Web for all and sundry to examine, use, extend, or dispute, along with the facts (expressed in RDF) the ontology is meant to organize. Anyone, anywhere on the Web could then take the facts and impose an alternative or rival organization upon them, or take both the facts and the ontology and refine the ontology to greater detail. In this way, the Semantic Web enables non-coordiated (and even non-cooperative) collaboration about a domain of discourse, one in which the conceptual work is aided and abetted by programs. Not only will our Web Agents find and aggregate information from the Web (and without fragile and error prone "scraping" of HTML pages), but they will be able to give some initial guidance about whether certain aggregations make sense.

Links

OWL standards documents

• OWL Web Ontology Language Overview, W3C Recommendation 10 February 2004.
• OWL Web Ontology Language Guide, W3C Recommendation 10 February 2004
• OWL Web Ontology Language Semantics and Abstract Syntax, W3C Recommendation 10 February 2004
• Dean M., Schreiber G (Editors); van Harmelen F., Hendler J., Horrocks I., McGuinness D.L., Patel-Schneider P.F., Stein L.A. (Authors), OWL Web Ontology Language Reference, W3C Recommendation, 10 February 2004. HTML

Short tutorials and introductions

• Wikipedia entry

• Introduction to OWL Web Ontology Language for Medical and Biosciences Applications

• Tutorial on OWL

• Introduction to OWL (W3Schools)

References

Clark, K., Parsia, B. and Hendler, J. (2004). Will the Semantic Web Change Education? Journal of Interactive Media in Education, 2004 (3). Special Issue on the Educational Semantic Web. ISSN:1365-893X [http:/www-jime.open.ac.uk/2004/3 www-jime.open.ac.uk/2004/3] (HTML)