End ALTERNATE.
Section MESS_ALT.
(* consequence sur la structure alternee *)
Variable b0 : Bag_of_Data Message.
Variable s0 : Site.

Lemma D_collect :
forall s1 s2 : Site,
D_queue (b0 s0 owner) -> D_queue (Collect_message Message b0 s1 s2 s0 owner).