End BACKWARD_SIMULATIONS.

(* Specifications: *)
Theorem backward_simulation_behavior_improves:
forall L1 L2, backward_simulation L1 L2 ->
forall beh2, program_behaves L2 beh2 ->
exists beh1, program_behaves L1 beh1 /\ behavior_improves beh1 beh2.
Corollary backward_simulation_same_safe_behavior:
forall L1 L2, backward_simulation L1 L2 ->
(forall beh, program_behaves L1 beh -> not_wrong beh) ->
(forall beh, program_behaves L2 beh -> program_behaves L1 beh).