{tt nth} returns the item in the list specified as its first
argument in the position specified as its second argument.
(Nth-Domain@Frame-Ontology Nth 2 Natural) (Nth-Domain@Frame-Ontology Nth 1 List)
(=> (= (Projection@Frame-Ontology ?Relation ?Column) ?Projection-Relation) (Forall (?Projection-Instance) (<=> (Instance-Of@Frame-Ontology ?Instance ?Projection-Relation) (Exists (?Tuple) (And (Member@Ol-User%Kif-Sets ?Tuple ?Relation) (= (Nth ?Tuple ?Column) ?Instance)))))) (=> (Nth-Domain@Frame-Ontology ?Relation ?N ?Type) (Forall (?Tuple) (=> (Member@Ol-User%Kif-Sets ?Tuple ?Relation) (And (>= (Length ?Tuple) ?N) (Instance-Of@Frame-Ontology (Nth ?Tuple ?N) ?Type)))))
(<=> (Projection@Frame-Ontology ?Relation ?Column) (And (Defined@Ol-User%Kif-Extensions (Arity@Frame-Ontology ?Relation)) (Positive-Integer@Ol-User%Kif-Extensions ?Column) (=< ?Column (Arity@Frame-Ontology ?Relation)) (Class@Frame-Ontology ?Projection-Relation) (Forall (?Projection-Instance) (<=> (Instance-Of@Frame-Ontology ?Instance ?Projection-Relation) (Exists (?Tuple) (And (Member@Ol-User%Kif-Sets ?Tuple ?Relation) (= (Nth ?Tuple ?Column) ?Instance))))))) (<=> (Nth-Domain@Frame-Ontology ?Relation ?N ?Type) (And (Defined@Ol-User%Kif-Extensions (Arity@Frame-Ontology ?Relation)) (Positive-Integer@Ol-User%Kif-Extensions ?N) (Class@Frame-Ontology ?Type) (Forall (?Tuple) (=> (Member@Ol-User%Kif-Sets ?Tuple ?Relation) (And (>= (Length ?Tuple) ?N) (Instance-Of@Frame-Ontology (Nth ?Tuple ?N) ?Type))))))