**Defined in theory: Kif-relations****Source code: frame-ontology.lisp**

**Documentation:**A function is a mapping from a domain to a range that associates a domain element with exactly one range element. The elements of the domain are tuples, as in relations. The range is a class -- a set of singleton tuples -- and element of the range is an instance of the class. Functions are also first-class objects in the same sense that relations are objects: namely, functions can be viewed as sets of tuples.

**Subclass-Of:**Relation

(<=> (Function ?Relation) (And (Relation ?Relation) (Forall (?Tuple1 ?Tuple2) (=> (Member ?Tuple1 ?Relation) (Member ?Tuple2 ?Relation) (= (Butlast ?Tuple1) (Butlast ?Tuple2)) (= (Last ?Tuple1) (Last ?Tuple2))))))