RDFS

RDFS (RDF Schema) is a simple ontology language that supports simple statements about classes and properties. Resources can be typed with a class via the rdf:type property; a class can be made a subclass of another via the rdfs:subClassOf property; a property can be made a subproperty of another via the rdfs:subPropertyOf property; and finally, properties can be given range and domains (as classes) via the rdfs:range and rdfs:domain properties, respectively.

Note that RDFS does not support any forms of negation, disjointness, etc. Therefore, a dataset augmented with an RDFS ontology cannot be inconsistent.

Furthermore, RDFS makes no clear separation between individuals, classes and properties (like OWL does). So a resource can e.g. be both a class and a property.

A sKWRL encoding of (most of) the RDFS semantics can be found here.

Guides and tutorials