Definition ag_nat : ageable nat :=
mkAgeable nat natLevel natAge1 ag_nat_facts.

(* Specifications: *)
Lemma nec_nat : forall (n n':nat),
@necR _ ag_nat n n' <-> n' <= n.
Lemma later_nat : forall (n n':nat),
@laterR _ ag_nat n n' <-> n' < n.