Definition internal_msg (tag : nat) (from to : nid) : bool :=
  coord_msg tag from to || participant_msg tag from to.

Lemma msg_specE_consume_external d i this tag m from from' to' tag' m' : internal_msg tag' from' to' -> E_consume_external d i this tag m from (fun d => msg_spec from' to' tag' m' (dsoup d)).