**Defined in ontology: Frame-ontology****Source pathname: /tmp_mnt/vol/q/htw/cms/ontolingua/examples/ontolingua/../../all-ontologies/ontolingua/frame-ontology.lisp****Also defined in:**Interface-ontology

**Arity:**2**Definition-Sort-Index@Interface-Ontology:***100***Documentation:**DOMAIN is short for ``domain restriction''. A domain restriction of a binary relation is a constraint on the exact-domain of the relation. A domain restriction is superclass of the exact-domain; that is, all instances of the exact-domain of the relation are also instances of the DOMAIN restriction. Thus, the DOMAIN of a relation is not unique.

In an ontology, specifying a domain restriction of a binary relation is a way to specify partial information about the objects to which the relation applies. For example, one can state that favorite-beer is a relation from beer drinkers to beers as (domain favorite-beer person). This says that all people who have

a favorite-beer are instances of person, even though there may be some instances of person who do not have a favorite beer.Representation systems can use these specifications to classify terms and check integrity constraints.

### Notes:

**See-Also:**In Cyc, domain is called makesSenseFor.

**Domain:**Binary-Relation**Instance-Of:**- Binary-Relation, Binary-Relation, Relation, Relation, Relation ...
**Inverse:**Domain-Of**Range:**Class

(=> (Domain ?Relation ?Restriction) (Subclass-Of (Exact-Domain ?Relation) ?Restriction))

(<=> (Domain ?Relation ?Restriction) (And (Binary-Relation ?Relation) (Class ?Restriction) (Subclass-Of (Exact-Domain ?Relation) ?Restriction)))

(Binary-Relation ?Relation)

**Domain:**Set

**Domain:**Relation

**Domain:**Bounded

**Domain:**Class

**Domain:**Number

**Domain:**Time-Point@Simple-Time