Inductive D_queue : queue Message -> Prop :=
  | D_empty : D_queue (empty Message)
  | D_dec :
      forall qm : queue Message,
      alternate qm -> D_queue (input Message dec qm).Inductive D_queue : queue Message -> Prop :=
  | D_empty : D_queue (empty Message)
  | D_dec :
      forall qm : queue Message,
      alternate qm -> D_queue (input Message dec qm).Inductive D_queue : queue Message -> Prop :=
  | D_empty : D_queue (empty Message)
  | D_dec :
      forall qm : queue Message,
      alternate qm -> D_queue (input Message dec qm).

Lemma D_post_dec : alternate (b0 s0 owner) -> D_queue (Post_message Message dec b0 s0 owner s0 owner).