Program Definition HO_pred_eq {T}{agT: ageable T}
(A: Type) (P: A -> pred T) (A': Type) (P': A' -> pred T) : pred nat :=
fun v => exists H: A=A',
match H in (_ = A) return (A -> pred T) -> Prop with
| refl_equal => fun (u3: A -> pred T) =>
forall x: A, (P x <=> u3 x) v
end P'.
Next Obligation.
intros; intro; intros.
destruct H0. exists x.
destruct x.
intros. specialize (H0 x). eapply pred_hereditary; eauto.
Qed.

Lemma necR_level:  forall w w' : rmap, necR w w' -> (level w >= level w')%nat.