Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Language standardisation

The Semantic Web is a vision for the future of the Web in which information is given explicit meaning, making it easier for machines to automatically process and integrate information available on the Web. The Semantic Web will build on XML's ability to define customized tagging schemes and RDF's flexible approach to representing data.

The first level above RDF required for the Semantic Web is an ontology language that can formally describe the meaning of terminology used in Web documents. If machines are expected to perform useful reasoning tasks on these documents, the language must go beyond the basic semantics of RDF Schema. In February 2004, the W3C released the Web Ontology Language OWL as a Recommendation. OWL is used to publish and share ontologies, supporting advanced Web search, software agents and knowledge management.

OWL 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.

The definition of OWL was motivated by a number of Use Cases (detailed in the OWL Use Cases and Requirements Document, which also provides more details on ontologies, and formulates design goals, requirements and objectives for OWL. OWL has been designed to meet the need for a Web Ontology Language and is part of the growing stack of W3C recommendations related to the Semantic Web.

- XML provides a surface syntax for structured documents, but imposes no semantic constraints on the meaning of these documents.

- XML Schema is a language for restricting the structure of XML documents and also extends XML with datatypes.

- RDF is a datamodel for objects ("resources") and relations between them, provides a simple semantics for this datamodel, and these datamodels can be represented in an XML syntax.

- RDF Schema is a vocabulary for describing properties and classes of RDF resources, with a semantics for generalization-hierarchies of such properties and classes.

- OWL 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.

WonderWeb provided significant input to the Standardisation process, with a number of project members serving on the working group. Implementations developed during the project (such as the OWL API and FaCT++) were also key inputs as

implementation experience to the standardisation process. The W3C requires that implementations are feasible before documents reach Recommendation status.

Key theoretical work (as reported in the publications) underpinning the standardisation process, and possible extensions was also contributed by WonderWeb members.

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