Section MESS_ALT.
(* consequence sur la structure alternee *)
Variable b0 : Bag_of_Data Message.
Variable s0 : Site.
(* no longer useful 'cos copy is out of band and could be last *)

Lemma alt_shuffle_copy2 :
forall q1 q2 : queue Message,
alternate (append Message q1 (input Message copy q2)) ->
alternate (append Message q1 q2).