RDF Schema
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RDF Schema (various abbreviated as RDFS, RDF(S), RDF-S, or RDF/S) is an extensible knowledge representation language, providing basic elements for the description of ontologies, otherwise called Resource Description Framework (RDF) vocabularies, intended to structure RDF resources. The first version[1] was published by the World-Wide Web Consortium (W3C) in April 1998, and the final[2] W3C recommendation was released in February 2004. Many RDFS components are included in the more expressive language Ontology Web Language (OWL).
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[edit] Main RDFS constructs
[edit] Classes and subclasses
- rdfs:Class allows to declare a resource as a class for other resources.
Typical example of an rdfs:Class is foaf:Person in the Friend of a Friend (FOAF) vocabulary. An instance of foaf:Person is a resource linked to the class using an rdf:type predicate, such as in the following formal expression of the natural language sentence : 'John is a Person'.
ex:John rdf:type foaf:Person
The definition of rdfs:Class is recursive: rdfs:Class is the rdfs:Class of any rdfs:Class.
- rdfs:subClassOf allows to declare hierarchies of classes.
For example, the following declares that 'Every Person is an Agent':
foaf:Person rdfs:subClassOf foaf:Agent
Hierarchies of classes support inheritance of a property domain and range (see definitions in next section) from a class to its subclasses.
[edit] Property domain and range
- rdfs:domain of an rdf:property declares the class of the subject in a triple using this property as predicate.
- rdfs:range of an rdf:property declares the class or datatype of the object in a triple using this property as predicate.
For example the following declarations are used to express that the property ex:employer is linking a subject which is a foaf:Person, to an object which is a foaf:Organization
ex:employer rdfs:domain foaf:Person
ex:employer rdfs:range foaf:Organization
Given the previous declarations, in the following triple, ex:John is necessarily a foaf:Person, and ex:CompanyX is necessarily a foaf:Organization
ex:John ex:employer ex:CompanyX
[edit] See also
- SPARQL Query Language for RDF
[edit] References
[edit] External links
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