Relation _CAVITY

A cavity is a hole inside an object (eg, a body part), say an internal hole (not connected to its host's complement.
Arity: 2
Domain: Region
Subrelation-Of: _hole
Axioms:
(=> (_Cavity ?A ?B)
    (Exists (?Z ?W ?K)
            (And (Material-Object ?Z)
                 (Region ?W)
                 (Host-Of ?Z ?W)
                 (Exists (?C)
                         (And (T-Complement ?Z ?C) (Identity ?K ?C)))
                 (Not (Connected ?A ?K)))))