The format of the NOCHILD operator is:
NOCHILD(Object, NotObject)
The purpose of the NOCHILD operator is to provide a NotSet for CheckParents when finding the parents of Object during parsing - the particular token may be known not to be a verb, but the parents of the object include verb forms (the "buildings" token is made a child of "building", for example). The use of NOCHILD prevents the use of paths out of Verb when finding parents.
The operator is normally only constructed for internal use.
See ONLYCHILD for an operator with a similar function.