Re: SUO: sorts, types and constraints

["John F. Sowa" <sowa@bestweb.net>]

Robert,

The 1998 draft of the KIF standard allows any monadic predicate
to be used as a type or sort constraint.  Following is the KIF
translation of the sentence "Every cat is on a mat" using
the 1998 notation for defining type or sort constraints:

  (forall ((?x cat)) (exists ((?y mat)) (on ?x ?y) ))

The KIF manual (Section 6.3) defines the semantics of
statement of this form by their translation to the
equivalent statements without any such constraints:

(forall (?x) (=> (cat ?x) (exists (?y)(and (mat ?y) (on ?x y) ))))

There is no syntactic distinction in KIF between monadic
predicates and sorts.  

John Sowa