--- /dev/null
+(**************************************************************************)
+(* ___ *)
+(* ||M|| *)
+(* ||A|| A project by Andrea Asperti *)
+(* ||T|| *)
+(* ||I|| Developers: *)
+(* ||T|| The HELM team. *)
+(* ||A|| http://helm.cs.unibo.it *)
+(* \ / *)
+(* \ / This file is distributed under the terms of the *)
+(* v GNU General Public License Version 2 *)
+(* *)
+(**************************************************************************)
+
+include "basic_2/notation/relations/lazypredsn_7.ma".
+include "basic_2/relocation/llpx_sn.ma".
+include "basic_2/reduction/cpx.ma".
+
+(* LAZY SN EXTENDED PARALLEL REDUCTION FOR LOCAL ENVIRONMENTS ***************)
+
+definition llpx: ∀h. sd h → genv → relation4 ynat term lenv lenv ≝
+ λh,g,G. llpx_sn (cpx h g G).
+
+interpretation "lazy extended parallel reduction (local environment, sn variant)"
+ 'LazyPRedSn G L1 L2 h g T d = (llpx h g G d T L1 L2).
+
+(* Basic inversion lemmas ***************************************************)
+
+lemma llpx_inv_flat: ∀h,g,I,G,L1,L2,V,T,d. ⦃G, L1⦄ ⊢ ➡[h, g, ⓕ{I}V.T, d] L2 →
+ ⦃G, L1⦄ ⊢ ➡[h, g, V, d] L2 ∧ ⦃G, L1⦄ ⊢ ➡[h, g, T, d] L2.
+/2 width=2 by llpx_sn_inv_flat/ qed-.
+
+(* Basic forward lemmas *****************************************************)
+
+lemma llpx_fwd_length: ∀h,g,G,L1,L2,T,d. ⦃G, L1⦄ ⊢ ➡[h, g, T, d] L2 → |L1| = |L2|.
+/2 width=4 by llpx_sn_fwd_length/ qed-.
+
+lemma llpx_fwd_flat_dx: ∀h,g,I,G,L1,L2,V,T,d. ⦃G, L1⦄ ⊢ ➡[h, g, ⓕ{I}V.T, d] L2 →
+ ⦃G, L1⦄ ⊢ ➡[h, g, T, d] L2.
+/2 width=3 by llpx_sn_fwd_flat_dx/ qed-.
+
+lemma llpx_fwd_pair_sn: ∀h,g,I,G,L1,L2,V,T,d. ⦃G, L1⦄ ⊢ ➡[h, g, ②{I}V.T, d] L2 →
+ ⦃G, L1⦄ ⊢ ➡[h, g, V, d] L2.
+/2 width=3 by llpx_sn_fwd_pair_sn/ qed-.
+
+(* Note: this might be removed *)
+lemma llpx_fwd_bind_sn: ∀h,g,a,I,G,L1,L2,V,T,d. ⦃G, L1⦄ ⊢ ➡[h, g, ⓑ{a,I}V.T, d] L2 →
+ ⦃G, L1⦄ ⊢ ➡[h, g, V, d] L2.
+/2 width=4 by llpx_sn_fwd_bind_sn/ qed-.
+
+(* Note: this might be removed *)
+lemma llpx_fwd_bind_dx: ∀h,g,a,I,G,L1,L2,V,T,d. ⦃G, L1⦄ ⊢ ➡[h, g, ⓑ{a,I}V.T, d] L2 →
+ ⦃G, L1.ⓑ{I}V⦄ ⊢ ➡[h, g, T, ⫯d] L2.ⓑ{I}V.
+/2 width=2 by llpx_sn_fwd_bind_dx/ qed-.
+
+(* Note: this might be removed *)
+lemma llpx_fwd_flat_sn: ∀h,g,I,G,L1,L2,V,T,d. ⦃G, L1⦄ ⊢ ➡[h, g, ⓕ{I}V.T, d] L2 →
+ ⦃G, L1⦄ ⊢ ➡[h, g, V, d] L2.
+/2 width=3 by llpx_sn_fwd_flat_sn/ qed-.
+
+(* Basic properties *********************************************************)
+
+lemma llpx_lref: ∀h,g,I,G,L1,L2,K1,K2,V1,V2,d,i. d ≤ yinj i →
+ ⇩[i] L1 ≡ K1.ⓑ{I}V1 → ⇩[i] L2 ≡ K2.ⓑ{I}V2 →
+ ⦃G, K1⦄ ⊢ ➡[h, g, V1, 0] K2 → ⦃G, K1⦄ ⊢ V1 ➡[h, g] V2 → ⦃G, L1⦄ ⊢ ➡[h, g, #i, d] L2.
+/2 width=9 by llpx_sn_lref/ qed.
+
+lemma llpx_refl: ∀h,g,G,T,d. reflexive … (llpx h g G d T).
+/2 width=1 by llpx_sn_refl/ qed.