An opening is a hole which connects two holes within two distinct objects; eg, in anatomy, it can exist by default in the organism or there can be another object regulating its existence in time (eg, pilorum, glottis).
(=> (_Opening ?A ?B) (Exists (?X ?Y ?Z ?W) (And (Hole-In ?X ?Z) (Hole-In ?Y ?W) (Different ?Z ?W) (Connects ?A ?X ?Y))))