Section DEL_EFFECT.
(* invariants *)
Variable c0 : Config.
Variable s0 : Site.
Hypothesis rt_true : rt c0 s0 = true.

Lemma del_trans_diff_site :
forall s3 s4 : Site,
(In_queue Message copy (bm c0 s3 s4) -> s3 <> s4) ->
In_queue Message copy (bm (delete_trans c0 s0) s3 s4) -> s3 <> s4.