(** ** Provability *)
Hint Resolve enc_vars.
Definition ctx_S :=
F3 :: rev F2 ++ rev F1.

(* Specifications: *)
Lemma drv_prv s u v :
derivable R u v -> (@prv s b ctx_S (Pr (enc u) (enc v))).
Lemma impl_prv s A B phi :
@prv s b (rev B ++ A) phi -> @ prv s b A (B ==> phi).
Lemma BPCP_prv' s :
BPCP' R -> @prv s b nil F.