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Last modified: February 10, 2004
OWL Web Ontology Language

OWL (Ontology Web Language) is being developed by the W3C Web Ontology Working Group. Six OWL specifications were published as W3C Recommendations in February 2004.

[February 10, 2004]   W3C Recommendations: Resource Description Framework (RDF) and Web Ontology Language (OWL).    The World Wide Web Consortium has announced "final approval of two key Semantic Web technologies, the revised Resource Description Framework (RDF) and the Web Ontology Language (OWL). RDF and OWL are Semantic Web standards that provide a framework for asset management, enterprise integration and the sharing and reuse of data on the Web. These standard formats for data sharing span application, enterprise, and community boundaries, since different types of users can share the same information even if they don't share the same software." The Resource Description Framework (RDF) is a "language for representing information about resources in the World Wide Web. It is particularly intended for representing metadata about Web resources, such as the title, author, and modification date of a Web page, copyright and licensing information about a Web document, or the availability schedule for some shared resource. However, by generalizing the concept of a 'Web resource', RDF can also be used to represent information about things that can be identified on the Web, even when they cannot be directly retrieved on the Web. Examples include information about items available from on-line shopping facilities (e.g., information about specifications, prices, and availability), or the description of a Web user's preferences for information delivery." The W3C RDF Recommendation is presented six parts: Primer, Concepts, Syntax, Semantics, Vocabulary, and Test Cases. 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 can be used to explicitly represent the meaning of terms in vocabularies and the relationships between those terms. This representation of terms and their interrelationships is called an ontology. OWL has more facilities for expressing meaning and semantics than XML, RDF, and RDF-S, and thus OWL goes beyond these languages in its ability to represent machine interpretable content on the Web. OWL is a revision of the DAML+OIL web ontology language incorporating lessons learned from the design and application of DAML+OIL." W3C has published the OWL Recommendation in six documents: Use Cases, Overview, Guide, Language Reference, Test Cases, and Language Semantics and Abstract Syntax.

[January 08, 2004]   Ontology Web Language for Services (OWL-S) Version 1.0.    OWL-S Version 1.0 has been released for public review by members of the OWL Services Coalition. OWL-S (formerly DAML-S) is "an OWL Web service ontology which supplies Web service providers with a core set of markup language constructs for describing the properties and capabilities of their Web services in unambiguous, computer-intepretable form." The OWL Web Ontology Language was published by W3C as a Proposed Recommendation on December 15, 2003. OWL is "used to publish and share sets of terms called ontologies, supporting advanced Web search, software agents, and knowledge management. It 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. OWL has three increasingly-expressive sublanguages: OWL Lite, OWL DL, and OWL Full." The OWL-based Web Service Ontology (OWL-S) Version 1.0 "features a number of refinements to the Service Profile and Process Model. The Service Profile is used to concisely represent the service in terms of capabilities, provenance, and operational parameters (e.g. cost-of-use, quality-of-service parameters, etc), for constructing both advertisements and requests. Version 1.0 offers clarification and simplification of capability description parameters (i.e., inputs, outputs, preconditions and effects), a tighter integration with the process model, and better organization/modularization of the Profile constructs."

[August 18, 2003]   W3C Releases Candidate Recommendations for Web Ontology Language (OWL).    The World Wide Web Consortium (W3C) has published a suite of six Candidate Recommendation specifications defining the Web Ontology Language (OWL). An emerging ontology standard designed to strengthen the Semantic Web foundations, OWL is "a language for defining structured, Web-based ontologies which enable richer integration and interoperability of data across application boundaries. Early adopters of these standards include bioinformatics and medical communities, corporate enterprise and governments. OWL enables a range of descriptive applications including managing web portals, collections management, content-based searches, enabling intelligent agents, web services and ubiquitous computing. OWL is already being used as an open standard for deploying large scale ontologies on the Web." The six Candidate Recommendation documents for OWL are written for different audiences, addressing variable needs in understanding and implementing the OWL language. These include: "(1) a presentation of the use cases and requirements that motivated OWL; (2) an overview document which briefly explains the features of OWL and how they can be used; (3) a comprehensive Guide that walks through the features of OWL with many examples of the use of OWL features; (4) a reference document that provides the details of every OWL feature; (5) a test case document, and test suite, providing over a hundred tests that can be used for making sure that OWL implementations are consistent with the language design; (6) a document presenting the semantics of OWL and details of the mapping from OWL to RDF." Public comment on the OWL CR documents is requested by 20-September-2003.

[April 04, 2003]   W3C Web Ontology Working Group Publishes Last Call Working Drafts.    W3C has announced the release of five Last Call Working Draft specifications for the OWL Web Ontology Language Version 1.0, together with an updated Test Cases document. OWL "is used to publish and share sets of terms called ontologies, providing advanced Web search, software agents and knowledge management. It is intended to provide a language that can be used to describe the classes and relations between them that are inherent in Web documents and applications. The Web Ontology Language OWL is a semantic markup language for publishing and sharing ontologies on the World Wide Web. OWL is developed as a vocabulary extension of RDF (the Resource Description Framework) and is derived from the DAML+OIL Web Ontology Language." According to WG Co-Chair Jim Hendler, the W3C working group has made a best effort attempt to address all comments received to date, and now seeks confirmation that the comments have been addressed to the satisfaction of the user community, allowing the WG to move forward with Proposed Recommendations following the Last Call process. Comments are due by May 9, 2003.

[November 08, 2002]   W3C Publishes Guide to the Web Ontology Language (OWL).    The W3C Web Ontology Working Group has produced a Version 1.0 working draft document Web Ontology Language (OWL) Guide documenting key concepts and uses of the OWL language. Building upon the foundations of the DAML+OIL specification, the W3C Web Ontology Language (OWL) "is intended to provide a language that can be used to describe the classes and relations between them that are inherent in Web documents and applications. The new Guide demonstrates the use of the OWL language (1) to formalize a domain by defining classes and properties of those classes, (2) to define individuals and assert properties about them, and (3) to reason about these classes and individuals to the degree permitted by the formal semantics of the OWL language. Document sections are organized to present an incremental definition of a set of classes, properties and individuals, beginning with the fundamentals and proceeding to more complex language components." The development of the Web Ontology Language is motivated by a recognition that the World Wide Web "as it is currently constituted resembles a poorly mapped geography. Our insight into the documents and capabilities available are based on keyword searches, abetted by clever use of document connectivity and usage patterns. The sheer mass of this data is unmanageable without powerful tool support. In order to map this terrain more precisely, computational agents require machine-readable descriptions of the content and capabilities of web accessible resources. These descriptions must be in addition to the human-readable versions of that information."

[July 31, 2002]   W3C Web Ontology Working Group Releases Working Drafts for OWL Semantic Markup Language.    Three initial working draft documents on 'OWL' have been published by the W3C's Web-Ontology Working Group (WebOnt). OWL is a semantic markup language for publishing and sharing ontologies on the World Wide Web. OWL is derived from the DAML+OIL Web Ontology Language and builds upon the Resource Description Framework. The designers expect that OWL will support the use of automated tools which "can use common sets of terms called ontologies to power services such as more accurate Web search, intelligent software agents, and knowledge management." The OWL Web Ontology Language is being designed "in order to provide a language that can be used for applications that need to understand the content of information instead of just understanding the human-readable presentation of content. OWL facilitates greater machine readability of web content than XML, RDF, and RDF-S support by providing an additional vocabulary for term descriptions." The Feature Synopsis for OWL Lite and OWL introduces the OWL language. The OWL Web Ontology Language 1.0 Reference provides a systematic, compact and informal description of all the modelling primitives of OWL. An OWL knowledge base is a collection of RDF triples as defined in the RDF/XML Syntax Specification; OWL prescribes a specific meaning for triples that use the OWL vocabulary. The Language Reference document specifies which collections of RDF triples constitute the OWL vocabulary and what the prescribed meaning of such triples is. The OWL Web Ontology Language 1.0 Abstract Syntax document describes a high-level, abstract syntax for both OWL and OWL Lite, a subset of OWL; it also provides a mapping from the abstract syntax to the OWL exchange syntax. [Full context]

[March 08, 2002]   W3C Publishes Web Ontology Language Requirements Document.    The W3C Web Ontology Working Group has published an initial working draft document outlining requirements for the Ontology Web Language (OWL) 1.0 specification. The draft document "specifies usage scenarios, goals and requirements for a web ontology language. Automated tools can use common sets of terms called ontologies to power services such as more accurate Web search, intelligent software agents, and knowledge management." An 'ontology' in terms of the WG charter "defines the terms used to describe and represent an area of knowledge. Ontologies are used by people, databases, and applications that need to share domain information, where a domain is just a specific subject area or area of knowledge, like medicine, tool manufacturing, real estate, automobile repair, financial management, etc. Ontologies include computer-usable definitions of basic concepts in the domain and the relationships among them... An ontology formally defines a common set of terms that are used to describe and represent a domain. The WD specification motivates the need for a Web ontology language by describing six use cases. Some of these use cases are based on efforts currently underway in industry and academia, others demonstrate more long-term possibilities. The use cases are followed by design goals that describe high-level objectives and guidelines for the development of the language. These design goals will be considered when evaluating proposed features." [Full context]

Principal References

Articles, Papers, Technical Reports, News

  • [January 27, 2004] "OWL Web Ontology Language: Parsing OWL in RDF/XML." By Sean Bechhofer (University of Manchester). W3C Working Group Note. 21-January-2004. Produced by members of the W3C Web Ontology Working Group. Version URL: Latest version URL: "The OWL Semantics and Abstract Syntax document provides a characterisation of OWL ontologies in terms of an abstract syntax. This is a high level description of the way in which we can define the characteristics of classes and properties. In addition, S&AS gives a mapping to RDF triples. This tells us how such an abstract description of an OWL ontology can be transformed to a collection of RDF triples, which can then be represented in a concrete fashion using, for example RDF/XML. In order to parse an OWL-RDF file into some structure closer to the abstract syntax we need to reverse this mapping, i.e., determine what the class and property definitions were that lead to those particular triples. An OWL-RDF parser takes an RDF/XML file and attempts to construct an OWL ontology that corresponds to the triples represented in the RDF. This document describes a basic strategy that could be used in such a parser... Note that this is not intended as a complete specification, but hopefully provides enough information to point the way towards how one would build a parser that will deal with a majority of (valid) OWL ontologies..."

  • [January 16, 2004]   PML: Proof Markup Language for Semantic Web Services.    A technical report published by the Knowledge Systems Laboratory at Stanford University proposes a "Proof Markup Language (PML) which "provides an interlingua for capturing the information agents need to understand results and to justify why they should believe the results." The model and tools are predicated upon a conviction that successful inter-operation between components in non-trivial Web Services transactions is dependent upon those components having a shared understanding of the results that have passed between. "In order for Semantic Web services to explain their results, they need to be able to generate justifications of their results in an exchangeable, combinable format. PML addresses the issue of understanding and trusting results generated by web services. PML classes are OWL classes, and thus are subclasses of owl:Class. They are used to build OWL documents representing both proofs and proof provenance information. PML concepts therefore can be considered to be either proof level concepts or provenance level concepts." The report provides an overview of related work and introduces an Inference Web infrastructure that uses PML as the foundation for providing explanations of web services to end users.

  • [June 16, 2003] "OWL Web Ontology Language XML Presentation Syntax." By Masahiro Hori (Kansai University, formerly IBM Tokyo Research), Jérôme Euzenat, (INRIA Rhône-Alpes), and Peter F. Patel-Schneider (Bell Labs Research, Lucent Technologies). W3C Note 11-June-2003. Latest version URL: This document from the W3C Web Ontology Working Group "specifies XML presentation syntax for OWL, which is defined as a dialect similar to OWL Abstract Syntax [OWL Semantics]. It is not intended to be a normative specification. Instead, it represents a suggestion of one possible XML presentation syntax for OWL. The OWL language provides three increasingly expressive sublanguages: OWL Lite, OWL DL, and OWL Full. This document provides XML Schemas for XML presentation syntax corresponding to the three sublanguages. Each of the sublanguages is an extension of its simpler predecessor, and the following relations hold but the inverses do not. [That is:] Every document valid against the XML Schema of OWL Lite is valid against the XML Schema of OWL DL; Every document valid against the XML Schema of OWL DL is valid against the XML Schema of OWL Full. Three Schemas are defined for the sublanguages: OWL Lite, OWL DL, and OWL Full; definitions of these Schemas are given in Appendix A..." Appendix B provides OWL Examples in XML Syntax.

  • [April 17, 2003] "Why Use OWL." By Adam Pease (Teknowledge). From xFront XML Collection (April 2003). "When you tell a person something, he can combine the new fact with an old one and tell you something new. When you tell a computer something in XML, it may be able to tell you something new in response, but only because of some other software it has that's not part of the XML spec. That software could be implemented differently in systems that still conform to the XML spec. You might get different answers from those systems. If you tell a computer something new in OWL, it can give you new information, based entirely on the OWL standard itself. A certain set of conclusions are required from any system that conforms to OWL. Systems may be able to provide all sorts of additional services and responses beyond the requirements of the standard but a certain basic set of conclusions will always be required. OWL gives computers one extra small degree of autonomy that can help them do more useful work for people. A set of OWL statements by itself (and the OWL spec) can allow you to conclude another OWL statement whereas a set of XML statements, by itself (and the XML spec) does not allow you to conclude any other XML statements. To employ XML to generate new data, you need knowledge embedded in some procedural code somewhere, rather than explicitly stated, as in OWL..." See also from xFront (Mitre): (1) "Using OWL to Avoid Syntactic Rigor Mortis"; (2) "A Quick Introduction to OWL Web Ontology Language."

  • [March 10, 2003]   Draft Requirements Document on Topic Maps Published Subjects.    A posting from Bernard Vatant (Chair, OASIS Topic Maps Published Subjects TC) announces the publication of a final review working draft for Published Subjects: Introduction and Basic Requirements. The document provides an introduction to Published Subjects and specifies requirements and recommendations for publishers of PSI sets. The TC welcomes all relevant and knowledgeable comments from domain experts in information technology areas impacted by the requirements draft, viz., experts in RDF, Semantic Web, Controlled Vocabularies, and Ontologies; also Librarians, Taxonomists, and others who manage the legacy that is likely to provide the main source of Published Subjects. Published Subjects as defined in the draft Specification "provide an open, scaleable, URI-based method of identifying subjects of discourse. They cater for the needs of both humans and applications, and they provide mechanisms for ensuring confidence and trust on the part of users. Published Subjects are therefore expected to be of particular interest to publishers and users of ontologies, taxonomies, classifications, thesauri, registries, catalogues, and directories, and for applications (including agents) that capture, collate or aggregate information and knowledge." The OASIS Topic Maps Published Subjects Technical Committee has been chartered "to promote Topic Maps interoperability through the use of Published Subjects. A further goal is to promote interoperability between Topic Maps and other technologies that make explicit use of abstract representations of subjects, such as the Resource Description Framework (RDF), DAML+OIL, and the Web Ontology Language (OWL)."

  • [October 31, 2002] "Web Ontology Language (OWL) Test Cases." W3C Working Draft 24-October-2002. Edited by Jeremy J. Carroll (HP) and Jos De Roo (AGFA). Latest version URL: Produced by the members of the W3C Web-Ontology (WebOnt) Working Group. Part of the W3C Semantic Web Activity. The WD document "contains and presents test cases for the Web Ontology Language (OWL) approved by the Web Ontology Working Group. Many of the test cases illustrate the correct usage of the Web Ontology Language (OWL), and the formal meaning of its constructs. Other test cases illustrate the resolution of issues considered by the working group... OWL is used to publish and share sets of terms called ontologies, providing accurate Web search, intelligent software agents, and knowledge management... it facilitates greater machine readability of web content than XML, RDF, and RDF-S support by providing a additional vocabulary for term descriptions. The OWL Web Ontology Language is being designed by the W3C Web Ontology Working Group as a revision of the DAML+OIL web ontology language." This document is subsidiary to the other Web Ontology Language recommendation track documents, including OWL Web Ontology Language 1.0 Reference [W3C Working Draft 29 July 2002], OWL Web Ontology Language 1.0 Abstract Syntax [W3C Working Draft 29 July 2002], and OWL Formal Semantics. For an introduction to OWL, see Feature Synopsis for OWL Lite and OWL [W3C Working Draft 29 July 2002].

  • [August 01, 2002] "W3C Hails Semantic Web, Web Services Usage Scenarios." By Paul Krill. In InfoWorld (July 31, 2002). "The World Wide Web Consortium (W3C) on Wednesday [2002-07-31] detailed the release of working drafts of its OWL Web Ontology Language to enable development of the Semantic Web. The Semantic Web is intended to enable more structured, intelligent processes on the Internet, allowing, for example, the automatic lookup of flights and hotel information after a person confirms attendance at a meeting in a specific city, said Ian Jacobs, W3C spokesman, in New York. 'The whole idea of the semantic Web is when you say something, I need to know what you're talking about. The idea is we want computers to know things,' Jacobs said. He described development of the Web Ontology Language as being in its early stages. The OWL Web Ontology Language, in which OWL is to be construed as an acronym for Web Ontology Language, is being designed by the W3C Web Ontology Working Group. The intent is to provide a language that can be used for applications that need to understand content, instead of just human-readable presentation of content, according to W3C. As part of the Semantic Web, machine reability is boosted by XML, RDF, and RDF-S support by providing a vocabulary for term descriptions. The three working drafts released by W3C are entitled Feature Synopsis, Abstract Syntax, and Language Reference. W3C this week also released a working draft of its Web Services Architecture Usage Scenarios collection, which is intended to provide usage cases and scenarios for generation of Web services... Also, the W3C on August 26 [2002] is holding an event entitled, 'Forum on Security Standards for Web Services,' in Boston. At this event, which is to be part of the XML Web Services One Conference amd Expo, relationships will be explored between W3C and OASIS Web services and security specifications. OASIS is co-sponsoring the event..."

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