With the recent announcement of two key recommendations by the World Wide Web Consortium (W3C; http://www.w3.org), the "Semantic Web" has finally come of age. Final approval of the Resource Definition Framework (RDF) and the OWL Web Ontology Language (OWL) will allow content producers and libraries to base future products and services upon technologies that will provide more complete asset management, integration, sharing, and reuse of data on the Web. Developed over the course of several years, the approval of these recommendations moves Semantic Web technology from what has essentially been a large research project into an enterprise-grade platform for information exchange.
Tim Berners-Lee, the W3C director and inventor of the World Wide Web, said: "RDF and OWL make a strong foundation for Semantic Web applications. 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."
Semantic Web development has been an ongoing project, spearheaded by the W3C. The goal of the Semantic Web is to extend the current Web to one where information is given well-defined meaning, better enabling computers and people to work in cooperation. Some of the areas where this technology can be applied include resource discovery, cataloging and classification, as well as content rating to provide guidelines for audience applicability. More complex implementations of the technology make use of intelligent software agents to facilitate knowledge sharing and exchange, in addition to providing a mechanism for defining intellectual property rights and privacy preferences for both individual users as well as the privacy policies of a data creator or warehousing agent.
As the computing industry and the Web community at large accept recommendations of the W3C as Web standards, these recommendations carry considerable weight. The W3C is an international industry consortium with over 350 organizations as members. The primary focus of all W3C recommendations is to provide a stable specification designed to promote interoperability of Web technologies.
In this latest announcement, perhaps the better known of the two technologies is RDF, which provides a common framework for expressing and exchanging information between applications without loss of meaning. It is for this reason that many information professionals may not be familiar with RDF as it is used primarily in cases where information is processed by computer applications, rather than being displayed on a Web page.
As a language for representing information about resources on the Web, RDF is used to express metadata about Web resources. This metadata can be relatively simple, descriptive information, such as title or author. However, the ability to "abstract" the representation of a Web resource is where the real power of RDF is realized. This means that RDF can be used to express and explain the complex relationships between items that can be found on the Web. At an even further level of abstraction, RDF can be used to express information about resources that can be identified, but not directly retrieved, from the Web. Examples of this type of information are the circulation status of a book, the security permissions associated with a digital object, or the preferences of a user on a Web site.
Like RDF, OWL is intended primarily for use by application programs that need to process the content of information. In its general meaning, the word ontology simply means an explicit specification of a conceptualization. OWL is used to explicitly represent the meaning of terms in vocabularies and the relationships between those terms. Therefore, in this context, ontology is defined as a definition of the terms used to describe and represent an area of knowledge along with the explanation of how these terms relate to each other.
Ontologies can range from a simple taxonomy, such as a hierarchical directory, to descriptive metadata schemes, such as the Dublin Core, to much more complex logical relationships. The ability to develop ontologies through OWL is useful as it provides a standard mechanism for developing domain or subject-specific vocabularies that can be understood by computer applications. Because of this, OWL facilitates greater machine interpretability of Web content.
Ontologies are a fundamental building block of the emerging Semantic Web. While ontologies provide a standard way of structuring and defining the meaning of the metadata terms within a community, they also provide a means for representing the semantics of documents and enabling those semantics to be used by Web applications and intelligent agents. Through this ability, applications developed in the future could truly be intelligent and could work with data in ways that more closely parallel the processing methods of humans.
In announcing the final approval of both technology recommendations, RDF and OWL, the efforts of the W3C to enhance the availability of machine-understandable data on the Web has moved into a new era. A core principle of the W3C is that the Web can only reach its full potential when data can be shared and processed by automated tools as well as it is by people. Guided by a vision of the future where data on the Web are defined and linked so they can be used by machines, not just for display purposes, but also for automation, integration, and reuse of data across various applications, these technologies will help ensure the possibility of a bright future for intelligent (and intelligible) information on the Web.