intros; intro;
eapply
(NoMACSubChange s u (acl s) (objectSC s) (files s)
(directories s) (secmat s)).
generalize H; elim s; simpl in |- *; auto.
Qed.

Lemma eq_scSym : forall a b : SecClass, eq_sc a b -> eq_sc b a.
unfold eq_sc in |- *; intros.