Section COPY_ALT.
(* structure de file d'attente *)
Variable c0 : Config.
Variable s0 s1 s2 : Site.
Hypothesis s2_not_owner : s2 <> owner.

Lemma copy_trans_D :
D_queue (bm c0 s0 owner) -> D_queue (bm (copy_trans c0 s1 s2) s0 owner).