RDF Schema

RDF Schema is a set of classes with certain properties using the RDF extensible knowledge representation data model, providing basic elements for the description of ontologies, otherwise called RDF vocabularies, intended to structure RDF resources. These resources can be saved in a triplestore to reach them with the query language SPARQL.
The first version was published by the World-Wide Web Consortium in April 1998, and the final W3C recommendation was released in February 2004. Many RDFS components are included in the more expressive Web Ontology Language.

Main RDFS constructs

RDFS constructs are the RDFS classes, associated properties and utility properties built on the limited vocabulary of RDF.


A typical example of an rdfs:Class is foaf:Person in the Friend of a Friend 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 class of classes, and so it is an instance of itself.
rdfs:Class rdf:type rdfs:Class
The other classes described by the RDF and RDFS specifications are:
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 .
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, from the triple:
ex:John ex:employer ex:CompanyX
can be inferred that ex:John is a foaf:Person, and ex:CompanyX is a foaf:Organization.
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 from a class to its subclasses.
Popular RDF vocabularies represented in RDFS include:
An entailment regime defines by using RDFS not only which entailment relation is used, but also which queries and graphs are well-formed for the regime. The RDFS entailment is a standard entailment relation in the semantic web.
For example, the following declares that 'Dog1 is an animal','Cat1 is a cat', 'Zoos host animals' and 'Zoo1 hosts the Cat2' :

ex:dog1 rdf:type ex:animal
ex:cat1 rdf:type ex:cat
zoo:host rdfs:range ex:animal
ex:zoo1 zoo:host ex:cat2

But this graph is not well formed because the system can not guess that a cat is an animal. We have to add 'Cats are animals' to do a well-formed graph with :

ex:cat rdfs:subClassOf ex:animal

Here is a correct example:
If your triplestore implements the regime entailment of RDF and RDFS, the SPARQL query as follows :

SELECT ?animal

Gives the following result with cat1 in it because the Cat's type inherits of Animal's type: