--- /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/unfold/sstas_lpss.ma".
+include "basic_2/computation/cprs_lpss.ma".
+include "basic_2/computation/dxprs.ma".
+
+(* DECOMPOSED EXTENDED PARALLEL COMPUTATION ON TERMS ************************)
+
+(* Properties about sn parallel substitution for local environments *********)
+
+lemma dxprs_lpss_conf: ∀h,g,L1,T,U1. ⦃h, L1⦄ ⊢ T •*➡*[g] U1 → ∀L2. L1 ⊢ ▶* L2 →
+ ∃∃U2. ⦃h, L2⦄ ⊢ T •*➡*[g] U2 & L1 ⊢ U1 ▶* U2.
+#h #g #L1 #T #U1 * #U #HTU #HU1 #L2 #HL12
+elim (sstas_lpss_conf … HTU … HL12) -HTU #U0 #HTU0 #HU0
+elim (cprs_cpss_conf … HU1 … HU0) -U #U #HU1 #HU0
+elim (cprs_lpss_conf_sn … HU0 … HL12) -HU0 -HL12 #U2 #HU2 #HU02
+lapply (cpss_trans … HU1 … HU2) -U /3 width=3/
+qed-.
+
+lemma dxprs_cpss_conf: ∀h,g,L,T1,U1. ⦃h, L⦄ ⊢ T1 •*➡*[g] U1 → ∀T2. L ⊢ T1 ▶* T2 →
+ ∃∃U2. ⦃h, L⦄ ⊢ T2 •*➡*[g] U2 & L ⊢ U1 ▶* U2.
+#h #g #L #T1 #U1 * #W1 #HTW1 #HWU1 #T2 #HT12
+elim (sstas_cpss_conf … HTW1 … HT12) -T1 #W2 #HTW2 #HW12
+elim (cprs_cpss_conf … HWU1 … HW12) -W1 /3 width=3/
+qed-.
+
+lemma dxprs_cpss_lpss_conf: ∀h,g,L1,T1,U1. ⦃h, L1⦄ ⊢ T1 •*➡*[g] U1 →
+ ∀T2. L1 ⊢ T1 ▶* T2 → ∀L2. L1 ⊢ ▶* L2 →
+ ∃∃U2. ⦃h, L2⦄ ⊢ T2 •*➡*[g] U2 & L1 ⊢ U1 ▶* U2.
+#h #g #L1 #T1 #U1 #HTU1 #T2 #HT12 #L2 #HL12
+elim (dxprs_cpss_conf … HTU1 … HT12) -T1 #U2 #HTU2 #HU12
+elim (dxprs_lpss_conf … HTU2 … HL12) -HTU2 -HL12 #U #HT2U #HU2
+lapply (cpss_trans … HU12 … HU2) -U2 /2 width=3/
+qed-.