RDFSchema

RDF Schema (RDFS) is a semantic extension of RDF that provides a lightweight vocabulary for describing resources and the relationships among them. It enables defining classes and properties, expressing basic hierarchies, and attaching metadata to RDF data, supporting simple inference and data integration across sources.

The RDFS vocabulary includes core resources such as rdfs:Resource, rdfs:Literal, rdfs:Class, rdfs:Property, and rdfs:Datatype. It also provides container-related terms like rdfs:Container and rdfs:ContainerMembershipProperty, along with descriptive properties such as rdfs:label, rdfs:comment, rdfs:seeAlso, and rdfs:isDefinedBy. The rdfs:member property relates containers to their members.

Key statements establish relationships between classes and properties: rdfs:subClassOf expresses subclass relations, and rdfs:subPropertyOf expresses subproperty relations. rdfs:domain and rdfs:range specify the expected class of subjects and objects for properties.

RDFS supports basic reasoning: if a resource is an instance of a class, and that class is a subclass of another class, the resource is also an instance of the superclass; domain and range constraints imply type information for property usage.

Limitations include limited expressive power compared with OWL; RDFS cannot express arbitrary constraints, cardinalities, or complex property characteristics. It is typically used for simple schemas and as a foundation for more expressive ontologies.

History and role: RDFS became a W3C Recommendation as part of the RDF family and remains a foundational element for semantic data on the Web, providing the basic mechanisms to describe resources and their relationships.