RDF Schema 1
RDF Schema
RDF Schema
Current Status Published
Year Started 1998
Editors Dan Brickley, Ramanathan V. Guha
Base Standards RDF
Related Standards OWL
Domain Semantic Web
Abbreviation RDFS
Website RDF Schema [1]
RDF Schema (variously abbreviated as RDFS, RDF(S), RDF-S, or RDF/S) is a set of classes with certain
properties using the RDF extensible knowledge representation language, providing basic elements for the description
of ontologies, otherwise called RDF vocabularies, intended to structure RDF resources. The first version[2] was
published by the World-Wide Web Consortium (W3C) in April 1998, and the final[3] W3C recommendation was
released in February 2004. Many RDFS components are included in the more expressive language Web Ontology
Language (OWL).
Main RDFS constructs
RDFS constructs are the RDFS classes, associated properties and utility properties built on the limited vocabulary of
RDF.
Classes
• rdfs:Resource is the class of everything. All things described by RDF are resources.
• rdfs:Class declares a resource as a class for other resources.
A 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 that is linked to the class foaf:Person using the rdf:type property, 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.
The other classes described by the RDF and RDFS specifications are:
• rdfs:Literal – literal values such as strings and integers. Property values such as textual strings are examples of
RDF literals. Literals may be plain or typed.
• rdfs:Datatype – the class of datatypes. rdfs:Datatype is both an instance of and a subclass of rdfs:Class. Each
instance of rdfs:Datatype is a subclass of rdfs:Literal.
• rdf:XMLLiteral – the class of XML literal values. rdf:XMLLiteral is an instance of rdfs:Datatype (and thus a
subclass of rdfs:Literal).
• rdf:Property – the class of properties.

RDF Schema 2
Properties
Properties are instances of the class rdf:Property and describe a relation between subject resources and object
resources. When used as such a property is a predicate (see also RDF: reification).
• rdfs:domain of an rdf:predicate declares the class of the subject in a triple whose second component is the
predicate.
• rdfs:range of an rdf:predicate declares the class or datatype of the object in a triple whose second component is
the predicate.
For example, the following declarations are used to express that the property ex:employer relates a subject,
which is of type foaf:Person, to an object, which is of type foaf:Organization:
ex:employer rdfs:domain foaf:Person
ex:employer rdfs:range foaf:Organization
Given the previous two declarations, the following triple requires that ex:John is necessarily a foaf:Person,
and ex:CompanyX is necessarily a foaf:Organization:
ex:John ex:employer ex:CompanyX
• rdf:type is a property used to state that a resource is an instance of a 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.
• rdfs:subPropertyOf is an instance of rdf:Property that is used to state that all resources related by one property
are also related by another.
• rdfs:label is an instance of rdf:Property that may be used to provide a human-readable version of a resource's
name.
• rdfs:comment is an instance of rdf:Property that may be used to provide a human-readable description of a
resource.
Utility Properties
• rdfs:seeAlso is an instance of rdf:Property that is used to indicate a resource that might provide additional
information about the subject resource.
• rdfs:isDefinedBy is an instance of rdf:Property that is used to indicate a resource defining the subject resource.
This property may be used to indicate an RDF vocabulary in which a resource is described.
References
[1] http:/ / www. w3. org/ TR/ rdf-schema/
[2] RDFS first version (http:/ / www. w3. org/ TR/ 1998/ WD-rdf-schema-19980409/ )
[3] Final W3C recommendation (http:/ / www. w3. org/ TR/ rdf-schema/ )