A user-defined rulebase possibly described by an external RDF-Schema An ontology class expression An additional statement about rdfs:Class An extension of the range of rdfs:subClassOf. An ontology slot constraint A generic number restriction expression. an abstract class of class types The class of primitive classes The class of defined classes A property connection between a slot constraint and a class expressions A property connection between a class definition and a slot constraint A property connection between an operator class expression and an operand class expression A property connection between a class expression and a slot expression A property connection between a class expression and a cardinality (integer) An expression corresponding to the conjunction of (two) class expressions An expression corresponding to the disjunction of (two) class expressions An expression corresponding to the negation of a class expression An expression corresponding to an existential slot constraint An expression corresponding to a universally quantified value restriction An ontology property expression corresponding to a (qualified) number restriction. An ontology property expression corresponding to a (qualified) number restriction. An ontology property expression corresponding to a (qualified) number restriction. A property connection between a property and the inverse property The class of all transitive relations. The class of all symmetric relations. The class of all reflexive relations.