(*
Lemma extends_fashionable : forall x y,
  R_extends x y -> fashionR x y.
Proof.
  intros.
  destruct x; destruct y; destruct H.
  subst v0.
  hnf in H.
  hnf; simpl.
  repeat rewrite knot_level.
  destruct (unsquash m); destruct (unsquash m0).
  simpl; intuition.
Qed.
*)


Definition knot_contracts := transp _ knot_extends.

Lemma knot_contracts_age_commute2 : forall x y z, knot_contracts x y /\ age y z -> exists y', age x y' /\ knot_contracts y' z.