Relation Can-Have-One

Instance-Of: Binary-Relation, Relation, Set
Arity: 2
A domain instance i CAN-HAVE-ONE value for a slot R if there is at most 1 value v for which R(i,v) holds.

Asserting (CAN-HAVE-ONE ?i R) in the definition of some class C, where ?i is the instance variable for that class, is another way of specifying that C is a domain restriction of R and R is a single-valued-slot on C.


Equivalence Axioms for Can-Have-One:

(<=> (Can-Have-One ?Instance ?Binary-Relation)
     (Has-At-Most ?Instance ?Binary-Relation 1))