World Wide Web Consortium Issues RDF and OWL Recommendations

Semantic Web emerges as commercial-grade infrastructure for sharing data on the Web

Today, the World Wide Web Consortium 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 – all of these different types of “user” can share the same information, even if they don’t share the same software.

Today’s announcement marks the emergence of the Semantic Web as a broad-based, commercial-grade platform for data on the Web. The deployment of these standards in commercial products and services signals the transition of Semantic Web technology from what was largely a research and advanced development project over the last five years, to more practical technology deployed in mass market tools that enables more flexible access to structured data on the Web. Testimonials from enterprise-scale implementors and independent developers illustrate current uses of these standards on the Web today.

“RDF and OWL make a strong foundation for Semantic Web applications,” said Tim Berners-Lee, W3C Director and inventor of the World Wide Web. “Their approval as W3C Recommendations come at a time when new products spring up in areas as diverse as Enterprise Integration and medical decision support. It’s not unlike the early days of the Web, when once people saw how it worked, they understood its power. We’re entering that phase now, where people can see the beginnings of the Semantic Web at work.”

A World Wide Web Consortium (W3C) Recommendation is understood by industry and the Web community at large as a Web standard. Each Recommendation is a stable specification developed by a W3C Working Group and reviewed by the W3C Membership. Recommendations promote interoperability of Web technologies of the Web by explicitly conveying the industry consensus formed by the Working Group.

Wide Range of Applications Growing from New Semantic Web Standards

Semantic Web-enabled software using RDF and OWL include:

• Content creation applications: Authors can connect metadata (subject, creator, location, language, copyright status, or any other terms) with documents, making the new enhanced documents searchable
• Tools for Web site management: Large Web sites can be managed dynamically according to content categories customized for the site managers
• Software that takes advantage of both RDF and OWL: Organizations can integrate enterprise applications, publishing and subscriptions using flexible models
• Cross-application data reuse: RDF and OWL formats are standard, not proprietary, allowing data reuse from diverse sources

Many specific examples of commercial applications and enterprise scale implementations of these technologies are detailed in both the testimonial page, and the RDF Implementations and OWL Implementations pages.

How the Semantic Web Pieces Fit Together – XML, RDF and OWL

Much has been written about the Semantic Web, as if it is a replacement technology for the Web we know today. “In reality,” countered Eric Miller, W3C Semantic Web Activity Lead, “it’s more Web Evolution than Revolution. The Semantic Web is made through incremental changes, by bringing machine-readable descriptions to the data and documents already on the Web. XML, RDF and OWL enable the Web to be a global infrastructure for sharing both documents and data, which make searching and reusing information easier and more reliable as well. ”

W3C’s Semantic Web Activity builds on work done in other W3C Activities, such as the XML Activity. Its focus is to develop standard technologies, on top of XML, that support the growth of the Semantic Web.

XML Provides Rules, Syntax for Structured Documents

At the foundation, XML provides a set of rules for creating vocabularies that can bring structure to both documents and data on the Web. XML gives clear rules for syntax; XML Schemas then serve as a method for composing XML vocabularies. XML is a powerful, flexible surface syntax for structured documents, but imposes no semantic constraints on the meaning of these documents.

RDF Delivers a Data Framework for the Web

RDF – the Resource Description Framework – is a standard a way for simple descriptions to be made. What XML is for syntax, RDF is for semantics – a clear set of rules for providing simple descriptive information. RDF Schema then provides a way for those descriptions to be combined into a single vocabulary. RDF is integrated into a variety of applications including:

• library catalogs
• world-wide directories
• syndication and aggregation of news, software, and content
• personal collections of music, photos, and events

In these cases, each uses XML as an interchange syntax. The RDF specifications provide a powerful framework for supporting the exchange of knowledge on the Web.

“RDF is part of the foundation of a major advance in the power of the Web. Ultimately, we will see users and applications combining information represented in RDF from multiple sources on the Web in ways that, until now, have been inconceivable,” explains Brian McBride, Chair of the RDF Core Working Group, “The RDFCore Working Group has turned the RDF specifications into both a practical and mathematically precise foundation on which OWL and the rest of the Semantic Web can be built.”

OWL Delivers Ontologies that Work on the Web

What’s needed next is a way to develop subject – or domain – specific vocabularies. That is the role of an ontology. An ontology defines the terms used to describe and represent an area of knowledge. Ontologies are used by people, databases, and applications that need to share subject-specific (domain) information – 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. They encode knowledge in a domain and also knowledge that spans domains. In this way, they make that knowledge reusable.

OWL – the Web Ontology Language – provides a language for defining structured, Web-based ontologies which delivers richer integration and interoperability of data among descriptive communities. Where earlier languages have been used to develop tools and ontologies for specific user communities (particularly in the sciences and in company-specific e-commerce applications), they were not defined to be compatible with the architecture of the World Wide Web in general, and the Semantic Web in particular.

OWL uses both URIs for naming and the description framework for the Web provided by RDF to add the following capabilities to ontologies:

• Ability to be distributed across many systems
• Scalability to Web needs
• Compatibility with Web standards for accessibility and internationalization
• Openness and extensibility

OWL builds on RDF and RDF Schema and adds more vocabulary for describing properties and classes: among others, relations between classes (e.g. disjointness), cardinality (e.g. “exactly one”), equality, richer typing of properties, characteristics of properties (e.g. symmetry), and enumerated classes.

“OWL takes a major step forward in representing and organizing knowledge on the World Wide Web. It strikes a sound balance between the needs of industry participants for a language which addresses their current Web use cases, and the restrictions on developing an ontology language that meshed with established scientific principles and research experience,” explained Jim Hendler and Guus Schreiber, co-chairs for the Web Ontology Working Group. “Over fifty Working Group members have successfully designed a language that addresses both sets of concerns and is endorsed by academics and practitioners alike.”

RDF and OWL Documents Include Primers, Use Cases, Test Suites, to Aid Developers

The W3C RDF Core Group has produced six documents. Each is aimed at different segments of those wishing to learn, use, implement or understand RDF. The RDF Primer is an introduction to, and tutorial on how to use, RDF and RDF Schema. RDF Concepts and Abstract Syntax specifies the fundamental concepts and information model of RDF. The RDF/XML Syntax Specification (Revised) defines how to write RDF in XML syntax. RDF Vocabulary Description Language 1.0: RDF Schema describes how to use RDF to describe application and domain specific vocabularies. RDF Semantics defines the mathematically precise formal semantics of RDF and RDF Schema. RDF Test Cases defines a set of test cases that illustrate aspects of the other specifications and may be used for the automatic testing of implementations.

The W3C Web Ontology Working Group has produced six OWL documents. Each is aimed at different segments of those wishing to learn, use, implement or understand the OWL language. Documents include – a presentation of the use cases and requirements that motivated OWL – an overview document which briefly explains the features of OWL and how they can be used – a comprehensive Guide that walks through the features of OWL with many examples of the use of OWL features – a reference document that provides the details of every OWL feature – 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 – a document presenting the semantics of OWL and details of the mapping from OWL to RDF.

Industrial and Academic Leaders Move Semantic Web Standards Forward

The RDF Core Working Group is comprised of industrial and academic expertise, lending the depth of research and product implementation experience necessary for building a common description framework for the Web. Participants include representatives from Hewlett Packard, Nokia, IBM, AGFA, ILRT Institute for Learning and Research Technology at the University of Bristol, IWA International Webmasters Association and the University of West Florida. The RDF Core Working Group builds on the contributions of many other organization which developed the RDF Model and Syntax (1999 Recommendation) and RDF Schema (1999 Proposed Recommendation).

The W3C Web Ontology Working Group carries a complement of industrial and academic expertise, lending the depth of research and product implementation experience necessary for building a robust ontology language system. Participants include representatives from Agfa-Gevaert N. V; Daimler Chrysler Research and Technology; DARPA; Defense Information Systems Agency (DISA); EDS; Fujitsu; Forschungszentrum Informatik (FZI); Hewlett Packard Company; Ibrow; IBM; INRIA; Ivis Group; Lucent; University of Maryland; Mondeca; Motorola; National Institute of of Standards and Technology (NIST); Network Inference, Nokia; Philips, University of Southampton; Stanford University; Sun Microsystems; Unicorn Solutions along with invited experts from German Research Center for Artificial Intelligence (DFKI) Gmbh; the Interoperability Technology Association for Information Processing, Japan (INTAP); and the University of West Florida.

OWL brings together a number of groups that have been developing Web ontology languages over the past decade. OWL is based the DAML+OIL language, which was developed by an international team funded by the US Defense Advanced Research Projects Agency (DARPA) and the European Commission’s Information Science Technologies (IST) program. The documents released today represent the maturation of this work shaped by the members of the the World Wide Web Consortium.