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 empty_queue2 :
forall c : Config,
legal c ->
forall s1 s2 s : Site, s1 = s -> s2 = s -> bm c s1 s2 = empty Message.