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OWL - Web Ontology Language Date: 2008/03/06 11:43:55
Revision: 1.12

This is a brief overview of the subset of the OWLWeb Ontology Language - A W3C recommendation defining Ontologies (Class structures). language used for defining the PLCSProduct Life Cycle Support The project developing ISO 10303-239. The name of ISO 10303-239 (published by ISO in 2005). Reference DataReference Data is the collection of class definitions representing a concept used to specialize entities of the information model, to make the use of them semantically more precise. The classes are defined external to the information model and any data exchange file, and the term "External Reference Data" is therefore a synonym. and does not attempt to cover the entire language. OWL is an ontology modelling language layered over RDF (Resource Description Framework) that includes the following features:

OWL then pulls together the elements from these other W3CWorld Wide Web Consortium ( - The standards body for the web. standards and adds more powerful concepts for defining vocabularies, set theory concepts, individuals and the rest. Because of this layering, when written as RDF/XML the XML Namespaces associated with these other standards appear in OWL XML documents.

Which OWL level is used for PLCS Reference Data?

There are three kinds of OWL specified in the standard: OWL Lite, OWL DL and OWL Full. These allow levels of implementation and serve as a series of (what are essentially) "conformance class" for such implementations. OWL DL builds on OWL Lite, and OWL Full builds on OWL DL. PLCS has, because of practical considerations, elected to use OWL DL. The “DL” in OWL DL is “Description Logic”. There are reasoners and inference engines that understand DL but far fewer understand OWL Full. The software tools supporting OWL can report whether the ontology is DL or not.

OWL concepts

The core concepts in OWL used for specifying the PLCS Reference Data are:

How is OWL used to specify typical modelling concepts?

While OWL is similar in nature to other languages such as EXPRESS or UML, it has its own focus. Some of the concepts which modellers use in those languages are not available in OWL.


OWL Web Ontology Language Guide (

OWL Web Ontology Language Reference Guide (

OWL Web Ontology Language Overview (