intros.
cut (~ set_In u (ActReaders y) /\ ~ set_In u (ActWriters y)).
tauto.
auto.
Qed.

(* Specifications: *)
Lemma EqfSSC1 :
forall (s : SFSstate) (u u0 : SUBJECT) (sc : SecClass),
u <> u0 -> fSSC (subjectSC s) u0 = fSSC (chsubsc_SC s u sc) u0.