Inductive wf_state: state -> Prop :=
  | wf_state_intro: forall mu sigma tau,
      wf_moves mu -> wf_moves sigma -> wf_moves tau ->
      wf_state (State mu sigma tau).Inductive wf_state: state -> Prop :=
  | wf_state_intro: forall mu sigma tau,
      wf_moves mu -> wf_moves sigma -> wf_moves tau ->
      wf_state (State mu sigma tau).

Lemma dtransition_preserves_wf_state: forall st st', dtransition st st' -> wf_state st -> wf_state st'.