(*  NOT TRUE, because readable doesn't constraint NoneP ... Lemma readable_VAL: forall w l, readable l (w_m w) <-> exists sh, (VALspec sh l * TT) w.  *)

Lemma level_later {A} `{H : ageable A}: forall {w: A} {n': nat},
laterR (level w) n' ->
exists w', laterR w w' /\ n' = level w'.