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The natural [[acronym and initialism|acronym]] for ''Web Ontology Language'' would be ''WOL'' instead of ''OWL''. Although the character [[Owl (Winnie the Pooh)|Owl]] from [[Winnie the Pooh]] wrote his name ''WOL'', the acronym ''OWL'' was [http://lists.w3.org/Archives/Public/www-webont-wg/2001Dec/0169.html proposed] without reference to that character, as an easily pronounced acronym that would yield good logos, suggest wisdom, and honor [[William A. Martin]]'s ''One World Language'' [[Knowledge representation|KR]] project from the 1970s.
The natural [[acronym and initialism|acronym]] for ''Web Ontology Language'' would be ''WOL'' instead of ''OWL''. Although the character [[Owl (Winnie the Pooh)|Owl]] from [[Winnie the Pooh]] wrote his name ''WOL'', the acronym ''OWL'' was [http://lists.w3.org/Archives/Public/www-webont-wg/2001Dec/0169.html proposed] without reference to that character, as an easily pronounced acronym that would yield good logos, suggest wisdom, and honor [[William A. Martin]]'s ''One World Language'' [[Knowledge representation|KR]] project from the 1970s.

=== Adoption ===

A survey (published in 2006) of ontologies available on the web collected 688 OWL ontologies. Of these, 199 were OWL Lite, 149 were OWL DL and 337 OWL Full (by syntax). 19 ontologies had in excess of 2000 classes. The same survey collected 587 [[RDFS]] vocabulary.<ref>{{cite conference
|url=http://www.springerlink.com/conten/d642020004747767/
|title= A Survey of the Web Ontology Landscape
|last1=Wang |first1=Taowei David |authorlink1=Taowei David Wang
|last2=Parsia |first2=Bijan |authorlink2=Bijan Parsia
|last3=Hendler |first3=James |authorlink3=James Hendler
|date=2006
|publisher=Springer Berlin
|booktitle=The Semantic Web - ISWC 2006
|pages=682-694
|location=Heidelberg
|id={{ISBN|978-3-540-49029-6}}
|doi=10.1007/11926078_49
|conference=5th International Semantic Web Conference
|conferenceurl=http://iswc2006.semanticweb.org/}}</ref>


== Ontologies ==
== Ontologies ==

Revision as of 08:19, 18 April 2010

OWL Web Ontology Language
AbbreviationOWL
StatusPublished
Year started2002
EditorsJames Hendler, Guus Schreiber
Base standardsResource Description Framework, RDFS
DomainSemantic Web
WebsiteOWL Reference
OWL 2 Web Ontology Language
AbbreviationOWL 2
StatusPublished
Year started2008
EditorsW3C OWL Working Group
Base standardsResource Description Framework, RDFS
DomainSemantic Web
WebsiteOWL2 Overview

The Web Ontology Language (OWL) is a family of knowledge representation languages for authoring ontologies endorsed by the World Wide Web Consortium.[1] They are characterised by formal semantics and RDF/XML-based serializations for the Semantic Web. OWL has attracted both academic, medical and commercial interest.

In October 2007, a new W3C working group[2] was started to extend OWL with several new features as proposed in the OWL 1.1 member submission.[3] This new version, called OWL 2, soon found its way into semantic editors such as Protégé and semantic reasoners such as Pellet[4], RacerPro [5] and FaCT++[6]. W3C announced the new version on 27 October 2009.[7]

History

Early Ontology Languages

Further information: Knowledge_representation § History_of_knowledge_representation_and_reasoning

There is a long history of ontological development in philosophy and computer science. Since the 1990s, a number of research efforts have explored how the idea of knowledge representation (KR) from AI could be made useful on the World Wide Web. These included languages based on HTML (called SHOE), based on XML (called XOL, later OIL), and various frame-based KR languages and knowledge acquisition approaches.

Ontology Languages For The Web

The OWL Language is a research-based[8] revision of the DAML+OIL web ontology language. DAML+OIL was developed by a group called the "EU/US ad hoc Joint Working Group on Agent Markup Languages" which was jointly funded by the US Defense Advanced Research Projects Agency (DARPA) under the DAML program and the EU's IST funding project.

Web Standards

Web Ontology Working Group

The World Wide Web Consortium (W3C) created the Web Ontology Working Group which began work on November 1, 2001 chaired by James Hendler and Guus Schreiber. The first working drafts of the abstract syntax, reference and synopsis were published in July 2002. The OWL documents became a formal W3C recommendation on February 10, 2004 and the working group was disbanded on May 31, 2004.[9]

OWL Working Group

OWL 2, an extension and revision of the OWL Web Ontology Language developed by the W3C OWL Working Group, became a W3C recommendation in October 2009. OWL 2 introduces profiles to improve scalability in typical applications.[7].

Acronym

Why not be inconsistent in at least one aspect of a language which is all about consistency?

— Guus Schreiber, Why OWL and not WOL?[10]

The natural acronym for Web Ontology Language would be WOL instead of OWL. Although the character Owl from Winnie the Pooh wrote his name WOL, the acronym OWL was proposed without reference to that character, as an easily pronounced acronym that would yield good logos, suggest wisdom, and honor William A. Martin's One World Language KR project from the 1970s.

Adoption

A survey (published in 2006) of ontologies available on the web collected 688 OWL ontologies. Of these, 199 were OWL Lite, 149 were OWL DL and 337 OWL Full (by syntax). 19 ontologies had in excess of 2000 classes. The same survey collected 587 RDFS vocabulary.[11]

Ontologies

Further information: Ontology (information science)

Introduction

An ontology is an explicit specification of a conceptualization.

— Tom Gruber, A Translation Approach to Portable Ontology Specifications[12]

The data described by an OWL ontology is interpreted as a set of "individuals" and a set of "property assertions" which relate these individuals to each other. An OWL ontology consists of a set of axioms which place constraints on sets of individuals (called "classes") and the types of relationships permitted between them. These axioms provide semantics by allowing systems to infer additional information based on the data explicitly provided. A full introduction to the expressive power of the OWL language(s) is provided in the W3C's OWL Guide.

Example

An ontology describing families might include axioms stating that a "hasMother" property is only present between two individuals when "hasParent" is also present, and individuals of class "HasTypeOBlood" are never related via "hasParent" to members of the "HasTypeABBlood" class. If it is stated that the individual Harriet is related via "hasMother" to the individual Sue, and that Harriet is a member of the "HasTypeOBlood" class, then it can be inferred that Sue is not a member of "HasTypeABBlood".

Semantics

Relation to description logics

In the beginning, IS-A was quite simple. Today, however, there are almost as many meanings for this inheritance link as there are knowledge-representation systems.

— Ronald J. Brachman, What ISA is and isn't[13]

Early attempts to build large ontologies were plagued by a lack of clear definitions. Members of the OWL family have model theoretic formal semantics, and so have strong logical foundations.

Description logics (DLs) are a family of logics that are decidable fragments of first-order logic with attractive and well-understood computational properties. OWL DL and OWL Lite semantics are based on DLs[14]. They combine a syntax for describing and exchanging ontologies, and formal semantics that gives them meaning. For example, OWL DL corresponds to the SHOIN (D) description logic, while OWL 2 corresponds to the SROIQ(D) logic. Sound, complete, terminating reasoners (i.e. systems which are guaranteed to derive every consequence of the knowledge in an ontology) exist for these DLs.

OWL Full is intended to be compatible with RDF Schema (RDFS), and to be capable of augmenting the meanings of existing Resource Description Framework (RDF) vocabulary. [15] A model theory describes the formal semantics for RDF. [16] This interpretation provides the meaning of RDF and RDFS vocabulary. So, the meaning of OWL Full ontologies are defined by extension of the RDFS meaning, and OWL Full is a semantic extension of RDF. [17]

Species

OWL Sublanguages

The W3C-endorsed OWL specification includes the definition of three variants of OWL, with different levels of expressiveness. These are OWL Lite, OWL DL and OWL FULL (ordered by increasing expressiveness). Each of these sublanguages is a syntactic extension of its simpler predecessor. The following set of relations hold. Their inverses do not.

  • Every legal OWL Lite ontology is a legal OWL DL ontology.
  • Every legal OWL DL ontology is a legal OWL Full ontology.
  • Every valid OWL Lite conclusion is a valid OWL DL conclusion.
  • Every valid OWL DL conclusion is a valid OWL Full conclusion.
OWL Lite

OWL Lite was originally intended to support those users primarily needing a classification hierarchy and simple constraints. For example, while it supports cardinality constraints, it only permits cardinality values of 0 or 1. It was hoped that it would be simpler to provide toolsupport for OWL Lite than its more expressive relatives, allowing quick migration path for systems utilizing thesauri and other taxonomies. In practice, however, most of the expressiveness constraints placed on OWL Lite amount to little more than syntactic inconveniences: most of the constructs available in OWL DL can be built using complex combinations of OWL Lite features. Development of OWL Lite tools has thus proven almost as difficult as development of tools for OWL DL, and OWL Lite is not widely used.

OWL DL

OWL DL was designed to provide the maximum expressiveness possible while retaining computational completeness (either φ or ¬φ belong), decidability (there is an effective procedure to determine whether φ is derivable or not), and the availability of practical reasoning algorithms. OWL DL includes all OWL language constructs, but they can be used only under certain restrictions (for example, number restrictions may not be placed upon properties which are declared to be transitive). OWL DL is so named due to its correspondence with description logic, a field of research that has studied the logics that form the formal foundation of OWL.

OWL Full

OWL Full is based on a different semantics from OWL Lite or OWL DL, and was designed to preserve some compatibility with RDF Schema. For example, in OWL Full a class can be treated simultaneously as a collection of individuals and as an individual in its own right; this is not permitted in OWL DL. OWL Full allows an ontology to augment the meaning of the pre-defined (RDF or OWL) vocabulary. It is unlikely that any reasoning software will be able to support complete reasoning for OWL Full.

OWL2 Profiles

In OWL 2, there are three sublanguages of the language. OWL 2 EL is a fragment that has polynomial time reasoning complexity; OWL 2 QL is designed to enable easier access and query to data stored in databases; OWL 2 RL is a rule subset of OWL 2.

Open world assumption

OWL uses the open world assumption, in contrast to SQL and Prolog, which adopt the closed world assumption. Under this open world assumption, if a statement cannot be proved to be true using current knowledge, we cannot draw the conclusion that the statement is false.

Terminology

OWL provides the capability of creating classes, properties, defining instances and its operations.

Classes

A class is a collection of objects. It corresponds to a Description Logic concept.

User-defined classes which are subclasses of root class owl:Thing. A class may contain individuals, which are instances of the class, and other subclasses. For example, Employee could be the subclass of class owl:Thing while Dealer, Manager, and Labourer all subclass of Employee.

Properties

A property is a directed binary relation that specifies class characteristics. It corresponds to a Description Logic role. They are attributes of instances and sometimes act as data values or link to other instances. Properties may possess logical capabilities such as being transitive, symmetric, inverse and functional. Properties may also have domains and ranges.

Datatype Properties

Datatype properties are relations between instances of classes and RDF literals or XML schema datatypes. For example, modelName (String datatype) is the property of Manufacturer class.

Object Properties

Object properties are relations between instances of two classes. For example, ownedBy may be an object type property of the Vehicle class and may have a range which is the class Person.

Instances

An instance is an object, and may belong to one or more classes. It corresponds to a Description Logic individual.

A class may have any number of instances. Instances are used to define the relationship among different classes. For example, if Mr. Smith is the instance of Manager Class and Mr. Shah is the instance of Dealer class then Mr. Smith is connected to Mr. Shah. by customer-dealer relationship. This is how OWL helps to establish various relationships among classes and instances of web content.

Operators

OWL supports various operations on classes such as union, intersection and complement. It also allows class enumeration, cardinality, and disjointness.

Public Ontologies

Pedagogic Examples

Libraries

Biomedical

General

Standards

Browsers

The following tools include public ontology browsers:

Search

Limitations

  • Relationships are directed
  • No direct language support for n-ary relationships. For example modelers may wish to describe the qualities of a relation, to relate more than 2 individuals or to relate an individual to a list. This cannot be done this within OWL. They may need to adopt a pattern instead which encodes the meaning outside the formal semantics.[25]

See also

References

  1. ^ Smith, Michael K. (2004-02-10). "OWL Web Ontology Language Guide". W3C. Retrieved 2008-07-15. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  2. ^ W3C working group
  3. ^ "Submission Request to W3C: OWL 1.1 Web Ontology Language". W3C. 2006-12-19.
  4. ^ Pellet
  5. ^ RacerPro
  6. ^ FaCT++
  7. ^ a b [1]
  8. ^ "Feature Synopsis for OWL Lite and OWL: W3C Working Draft 29 July 2002". W3C. 2002-07-29.
  9. ^ "Web-Ontology (WebOnt) Working Group (Closed)". W3C.
  10. ^ Ivan Herman. "Why OWL and not WOL?". Tutorial on Semantic Web Technologies. World Wide Web Consortium. Retrieved 18 April 2010.
  11. ^ Wang, Taowei David; Parsia, Bijan; Hendler, James (2006). "A Survey of the Web Ontology Landscape". The Semantic Web - ISWC 2006. 5th International Semantic Web Conference. Heidelberg: Springer Berlin. pp. 682–694. doi:10.1007/11926078_49. ISBN 978-3-540-49029-6. {{cite conference}}: External link in |conferenceurl= (help); Unknown parameter |booktitle= ignored (|book-title= suggested) (help); Unknown parameter |conferenceurl= ignored (|conference-url= suggested) (help)
  12. ^ Tom Gruber (1993). "A Translation Approach to Portable Ontology Specifications". In: Knowledge Acquisition. 5: 199-199.
  13. ^ Brachman, R.J. (1983). What ISA is and isn't: An analysis of taxonomic links in semantic networks. IEEE Computer 16(10), 30-36.
  14. ^ Ian Horrocks & Peter F. Patel-Schneider. "Reducing OWL Entailment to Description Logic Satisfiability" (PDF).
  15. ^ Deborah McGuinness and Frank van Harmelen (10 February 2004). "OWL Web Ontology Language Overview". W3C Recommendation for OWL, the Web Ontology Language. World Wide Web Consortium. Retrieved 18 April 2010.
  16. ^ Patrick Hayes (10 February 2004). "RDF Semantics". Resource Description Framework. World Wide Web Consortium. Retrieved 18 April 2010.
  17. ^ Peter F. Patel-Schneider,Patrick Hayes and Ian Horrocks (10 February 2004). "OWL Web Ontology Language Semantics and Abstract Syntax Section 5. RDF-Compatible Model-Theoretic Semantics". W3C Recommendation for OWL, the Web Ontology Language. World Wide Web Consortium. Retrieved 18 April 2010. {{cite web}}: line feed character in |title= at position 26 (help)
  18. ^ OBO Foundry
  19. ^ OBO Download Matrix
  20. ^ NCBO BioPortal
  21. ^ TONES (Thinking ONtologiES)
  22. ^ SUMO download
  23. ^ TDWG LSID Vocabularies
  24. ^ Protégé web site
  25. ^ Natasha Noy and Alan Rector (12 April 2006). "Defining N-ary Relations on the Semantic Web". World Wide Web Consortium. Retrieved 17 April 2010.

External links

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