Section MESSAGE.
(* as formulated by Jean *)
(* As I need it in my proof *)
(* The proof is long and very boring, but it is a simple case analysis.  Could it be possible to simplify it? *)

Lemma not_reflexive :
forall c : Config,
legal c ->
forall s1 s5 : Site,
In_queue Message (inc_dec s1) (bm c s5 owner) -> s1 <> s5.