W3C

Feature Synopsis for OWL Lite and OWL

This version:
23 June 2002
Previous version:
26 May 2002
15 May 2002
13 May 2002
Editors:
Deborah L. McGuinness (Knowledge Systems Laboratory, Stanford University )
dlm@ksl.stanford.edu
Frank van Harmelen (Free University, Amsterdam)
frank.van.harmelen@cs.vu.nl


Abstract

The OWL Web Ontology Language is being designed by the W3C Web Ontology Working Group in order to provide a language that can be used for applications that need to understand the logical content of information instead of just understanding the human-readable presentation of content. The OWL language can be used to allow the explicit representation of term vocabularies and the relationships between entities in these vocabularies. In this way, the language goes beyond XML, RDF and RDF-S in allowing greater machine readable content on the web. The OWL language is a revision of the DAML+OIL web ontology language. This document provides an introduction to the OWL language by providing a motivation, language synopsis, language description with simple examples, and discussion section first on a a simpler version of the full OWL language called OWL lite and then on the full OWL language. A more complete language description will be provided in accompanying documents. For a more detailed introduction to both OWL and OWL lite, please see the OWL reference description document and the Formal Specification of the OWL Web Ontology Language.

Table of contents

  1. Motivation
  2. Language Synopsis
    1. OWL Lite Synopsis
      1. OWL Lite RDF Schema Features Synopsis
      2. OWL Lite Equality and Inequality Synopsis
      3. OWL Lite Property Characteristics Synopsis
      4. OWL Lite Restricted Cardinality Synopsis
      5. OWL Lite Datatypes Synopsis
      6. OWL Lite Header Information Synopsis
    2. OWL Synopsis
      1. OWL Class Axioms Synopsis
      2. OWL Boolean Combinations of Class Expressions Synopsis
      3. OWL Arbitrary Cardinality synopsis
      4. OWL Filler Information Synopsis
  3. Language Description of OWL Lite
    1. OWL Lite RDF Schema Features Description
    2. OWL Lite Equality and Inequality Description
    3. OWL Lite Property Characteristics Description
    4. OWL Lite Restricted Cardinality Description
    5. OWL Lite Datatypes
    6. OWL Lite Header Information
  4. Incremental Language Description of OWL
  5. Summary
  6. Status

1. Motivation

The goal of this document is to provide a simple introduction to the Ontology Web Language. This document begins by describing a subset of the entire language called OWL Lite. The goal of OWL Lite is to provide a language that is viewed by tool builders to be easy enough and useful enough to support. One expectation is that tools will facilitate the widespread adoption of OWL and thus OWL language designers should attempt to create a language that tool developers will flock to. An easy language implies that the language should be:

A useful language implies that the language should be:

While it is widely appreciated that all of the features in languages such DAML+OIL are important to some users, it is also understood that a languages as expressive as DAML+OIL may be daunting to some groups who are trying to support a tool suite for the entire language. In order to provide a target that is approachable to a wider audience, a subgroup of the web ontology working group was formed to propose a smaller language now referred to as OWL Lite.

This smaller language attempts to capture many of the commonly used features of OWL and DAML+OIL. It also attempts to describe a useful language that provides more than RDFS with the goal of adding functionality that is important in order to support web applications. It also attempts to choose features that do not impose too many restrictions on toolbuilders who want to extend their support beyond this "lite" language.

This document also provides an introduction to the full OWL language by introducing the additional features in OWL over those included in OWL Lite.

The only main difference between this version of OWL Lite and the previous description is a limitation on cardinalities and the explicit inclusion of inverseFunctional for properties. The document has changed in that it now describes both OWL lite as well as the full OWL language.

2 Language Synopsis

This section contains the language synopsis for OWL Lite and OWL.

2.1 OWL Lite Synopsis

The expanded summary listing of OWL Lite is:

2.1.1 OWL Lite RDF Schema Features Synopsis

2.1.2 OWL Lite Equality and Inequality Synopsis

2.1.3 OWL Lite Property Characteristics Synopsis

2.1.4 OWL Lite Restricted Cardinality Synopsis

2.1.5 OWL Lite Datatypes Synopsis

2.1.6 OWL Header Information Synopsis

2.2 OWL Synopsis

The expanded summary listing of OWL adds the following:

2.2.1 OWL Class Axioms Synopsis

2.2.2 OWL Boolean Combinations of Class Expressions Synopsis

2.2.3 OWL Arbitrary Cardinality Synopsis

2.2.4 OWL Filler Information Synopsis


The next section contains an expanded description of the language.

3. Language Description of OWL Lite

This section will discuss the proposed language features in English. An abstract syntax is used for presentation of the language. OWL Lite has a subset of the full OWL language constructors and has a few restrictions. Unlike the full OWL language (and DAML+OIL), classes can not be defined in terms of arbitrary descriptions; instead only named superclasses and certain kinds of restrictions can be used. Equivalence for classes, and subclass between classes are all only allowed on named classes, not arbitrary descriptions. Similarly, property restrictions in OWL-Lite cannot have embedded descriptions, instead only allowing class names where descriptions would be allowed in Full OWL. It also has a limited notion of cardinality - the only cardinalities allowed to be explicitly stated are 0 or 1.

3.1 OWL Lite RDF Schema Features Description

The limited language can be viewed as an extension of a restricted view of the RDF language. The restrictions limit the set of allowable models. The implications of the restriction are that every statement valid in the language describable by this document will be valid RDF, but not all valid RDF will be valid in the language described by the document. It retains the following terms from RDF. These terms may be referred to as RDF: < TERM >.

3.2 OWL Lite Equality and Inequality Description

The following features related to equality or inequality are included:

3.3 OWL Lite Property Characteristics Description

3.4 OWL Lite Restricted Cardinality Description

3.5 OWL Lite Datatypes Description

3.6 OWL Lite Header Information Description

4. Incremental Language Description of OWL

Full OWL extends the constructions of OWL Lite with the following:

5. Summary

This document provides a high level description of the OWL language by providing a feature synopsis of both OWL Lite and the full language. It provides simple English descriptions of the constructors along with a simple example. It makes no attempt to include a syntax. It also provides pointers to the other related documents for more details. Previous versions of the document provided the historical view of the evolution of OWL Lite and the issues discussed in its evolution.

6. Status of this document

This section describes the status of this document at the time of its publication. Other documents may supersede this document.

This document is a working document for the use by W3C Members and other interested parties. It may be updated, replaced or made obsolete by other documents at any time.

This document has been produced as part of the W3C Semantic Web Activity, following the procedures set out for the W3C Process. The document has been compiled by the Web Ontology Working Group. The goals of the Web Ontology working group are discussed in the Web Ontology Working Group charter .

A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR/.