Definition notRel (n : nat) (R : naryRel n) : naryRel n.
intros.
induction n as [| n Hrecn].
exact (negb R).
simpl in |- *.
intros.
apply Hrecn.
apply (R H).
Defined.

Lemma notRelPR :
forall (n : nat) (R : naryRel n), isPRrel n R -> isPRrel n (notRel n R).