(* no longer useful 'cos copy is out of band and could be last *)

Lemma alt_post_inc_old :
forall s1 : Site,
alternate (b0 s0 owner) ->
b0 s0 owner = empty Message \/
last Message (b0 s0 owner) = value Message dec ->
alternate (Post_message Message (inc_dec s1) b0 s0 owner s0 owner).