Definition rooted_fun (s1 s2 : Site) (m : Message) :=
  match m with
  | copy => if eq_site_dec s1 s0 then 1%Z else 0%Z
  | dec => if eq_site_dec s2 s0 then 1%Z else 0%Z
  | inc_dec s3 =>
      if eq_site_dec s3 s0
      then
       if eq_site_dec s2 owner then 1%Z else 0%Z
      else 0%Z
  end.Definition rooted (s1 s2 : Site) (q : queue Message) :=
  reduce Message (rooted_fun s1 s2) q.Definition sigma_rooted (bm : Bag_of_message) :=
  sigma2_table Site LS LS (queue Message) rooted bm.

Lemma rooted_fun_positive_or_null : forall (s0 x y : Site) (a : Message), (rooted_fun s0 x y a >= 0)%Z.