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Broadly speaking, inference on the Semantic Web can be characterized by discovering new relationships. On the Semantic Web, data is modeled as a set of (named) relationships between resources. “Inference” means that automatic procedures can generate new relationships based on the data and based on some additional information in the form of a vocabulary, e.g., a set of rules. Whether the new relationships are explicitly added to the set of data, or are returned at query time, is an implementation issue.

On the Semantic Web, the source of such extra information can be defined via vocabularies or rule sets. Both of these approaches draw upon knowledge representation techniques. In general, ontologies concentrate on classification methods, putting an emphasis on defining 'classes', 'subclasses', on how individual resources can be associated to such classes, and characterizing the relationships among classes and their instances. Rules, on the other hand, concentrate on defining a general mechanism on discovering and generating new relationships based on existing ones, much like logic programs, like Prolog, do. In the family of Semantic Web related W3C Recommendations RDFS, OWL, or SKOS are the tools of choice to define ontologies, whereas RIF has been developed to cover rule based approaches.
See Also

Inference Web Project LogoInference Web
Principal Investigator: Deborah L. McGuinness
Description: The Inference Web is a Semantic Web based knowledge provenance infrastructure that supports interoperable explanations of sources, assumptions, learned information, and answers as an enabler for trust. Provenance - if users (humans and agents) are to use and integrate data from unknown, uncertain, or multiple sources, they need provenance metadata for evaluation Interoperability - more systems are using varied sources and multiple information manipulation engines, thus increasing interoperability requirements Explanation/Justification - if information has been manipulated (i.e., by sound deduction or by heuristic processes), information manipulation trace information should be available Trust - if some sources are more trustworthy than others, trust ratings are desired The Inference Web consists of two important components: Proof Markup Language (PML) Ontology - Semantic Web based representation for exchanging explanations including provenance information - annotating the sources of knowledge justification information - annotating the steps for deriving the conclusions or executing workflows trust information - annotating trustworthiness assertions about knowledge and sources IW Toolkit - Web-based and standalone tools that facilitate human users to browse, debug, explain, and abstract the knowledge encoded in PML.
Wineagent LogoWine Agent
Principal Investigator: Deborah L. McGuinness
Description: The Wine Agent represents knowledge of wines and foods and is a demonstration platform for a large variety of Semantic Web technologies in a rich domain and is derived from previous work in the field of reasoning systems.