t specialization of: #$FunctionalRelation  #$Predicate <br />
	    direct generalization of: #$StrictlyFunctionalPredicate #$FunctionalSlot</p>
<p>#$FunctionalSlot   predicates that is functional in its second argument</p>
<p>    A specialization of #$FunctionalPredicate each instance of which is a binary predicate that is functional in its second argument position. More precisely, a binary predicate PRED is an instance of #$FunctionalSlot if, for any legal occupant THING1 of PRED's first (or arg1