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

Lemma del_trans_st_rt :
forall s1 : Site,
st c0 s1 = 0%Z ->
rt c0 s1 = true ->
((st c0 s0 > 0)%Z -> rt c0 s0 = true) ->
(st (delete_trans c0 s1) s0 > 0)%Z -> rt (delete_trans c0 s1) s0 = true.