The W3C’s Semantic Web Best Practices and Deployment Working Group aims to “provide hands-on support for developers of Semantic Web applications.” Their approach is to develop and publish notes explaining good ways to tackle common KR problems in RDF and OWL. For example, given RDF’s underlying binary relations, what are good ways to encode the n-ary relationships needed by many domains? If you are building ontologies or just trying to understand how RDF and OWL should be used, you need to take a look at these.

The working group has published three new working drafts:

• SKOS Core Guide. “SKOS Core provides a model for expressing the basic structure and content of concept schemes (thesauri, classification schemes, subject heading lists, taxonomies, terminologies, glossaries and other types of controlled vocabulary).”
• SKOS Core Vocabulary Specification. This document gives a reference-style overview of the SKOS Core Vocabulary as it stands at the time of publication. It also describes the policies for ownership, naming, persistence and change by which the SKOS Core Vocabulary is managed.
• QuickGuide to Publishing a Thesaurus on the Semantic Web. “This document describes in brief how to express the content and structure of a thesaurus, and metadata about a thesaurus, in RDF.”

These join some very useful previous working group notes and working drafts, including the following:

• Representing Classes As Property Values on the Semantic Web. “This document addresses the issue of using classes as property values in OWL and RDF Schema. It is often convenient to put a class (e.g., Animal) as a property value (e.g., topic or book subject) when building an ontology. While OWL Full and RDF Schema do not put any restriction on using classes as property values, in OWL DL and OWL Lite most properties cannot have classes as their values. We illustrate the direct approach for representing classes as property values in OWL-Full and RDF Schema. We present various alternative mechanisms for representing the required information in OWL DL and OWL Lite.”
• Defining N-ary Relations on the Semantic Web: Use With Individuals. ” In Semantic Web languages, such as RDF and OWL, a property is a binary relation; that is, it links two individuals or an individual and a value. How do we represent relations among more than two individuals? How do we represent properties of a relation, such as our certainty about it, severity or strength of a relation, relevance of a relation, and so on? The document presents ontology patterns for representing n-ary relations and discusses what users must consider when choosing these patterns.”
• Representing Specified Values in OWL: “value partitions” and “value sets”. “Modelling various descriptive “features” (also known variously as “qualities”, “attributes” or “modifiers”) is a frequent requirement when creating ontologies. For example: “size” may describe persons or other physical objects and be constrained to take the values “small”, “medium” or “large”; rank may describe military officers and restricted to a specific list of values depending on the military organisation. In OWL such descriptive features are modelled as properties whose range specifies the constraints on the values that the property can take on. This document describes two methods to represent such features and their specified values: 1) as partitions of classes; and 2) as enumerations of individuals.”

Related posts: • New IST project on Ambient Intelligence Agents;  • W3C Rule Interchange Format WG publishes usecase and requirements study;  • SKOS: Simple Knowledge Organization System;  

Posted on Monday, May 23rd, 2005 at 10:54 am in categories [Ontologies, KR, Semantic Web]. Comments feed. Leave a response, or trackback from your own site. edit