--- /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/ltpss_sn_alt.ma".
+include "basic_2/unwind/sstas_ltpss_dx.ma".
+
+(* ITERATED STRATIFIED STATIC TYPE ASSIGNMENT FOR TERMS ************************)
+
+(* Properties about sn parallel unfold *****************************************)
+
+lemma sstas_ltpss_sn_conf: ∀h,g,L1,L2,d,e. L1 ⊢ ▶* [d, e] L2 →
+ ∀T,U1. ⦃h, L1⦄ ⊢ T •*[g] U1 →
+ ∃∃U2. L1 ⊢ U1 ▶* [d, e] U2 & ⦃h, L2⦄ ⊢ T •*[g] U2.
+#h #g #L1 #L2 #d #e #H
+lapply (ltpss_sn_ltpssa … H) -H #H @(ltpssa_ind … H) -L2 /2 width=3/
+#L #L2 #HL1 #HL2 #IHL1 #T #U1 #H1
+lapply (ltpssa_ltpss_sn … HL1) -HL1 #HL1
+lapply (ltpss_sn_dx_trans_eq … HL1 … HL2) -HL1 #HL12
+elim (IHL1 … H1) -IHL1 -H1 #U #HU1 #HTU
+elim (sstas_ltpss_dx_conf … HTU … HL2) -HTU -HL2 #U2 #H2 #HU2
+lapply (ltpss_sn_tpss_trans_eq … HU2 … HL12) -HU2 -HL12 #HU2
+lapply (tpss_trans_eq … HU1 HU2) -U /2 width=3/
+qed.
+
+lemma sstas_ltpss_sn_tpss_conf: ∀h,g,L1,T1,U1. ⦃h, L1⦄ ⊢ T1 •*[g] U1 →
+ ∀L2,d,e. L1 ⊢ ▶* [d, e] L2 →
+ ∀T2. L2 ⊢ T1 ▶* [d, e] T2 →
+ ∃∃U2. ⦃h, L2⦄ ⊢ T2 •*[g] U2 &
+ L1 ⊢ U1 ▶* [d, e] U2.
+#h #g #L1 #T1 #U1 #HTU1 #L2 #d #e #HL12 #T2 #HT12
+elim (sstas_ltpss_sn_conf … HL12 … HTU1) -HTU1 #U #HU1 #HT1U
+elim (sstas_tpss_conf … HT1U … HT12) -T1 #U2 #HTU2 #HU2
+lapply (ltpss_sn_tpss_trans_eq … HU2 … HL12) -HU2 -HL12 #HU2
+lapply (tpss_trans_eq … HU1 HU2) -U /2 width=3/
+qed.
+
+lemma sstas_ltpss_sn_tps_conf: ∀h,g,L1,T1,U1. ⦃h, L1⦄ ⊢ T1 •*[g] U1 →
+ ∀L2,d,e. L1 ⊢ ▶* [d, e] L2 →
+ ∀T2. L2 ⊢ T1 ▶ [d, e] T2 →
+ ∃∃U2. ⦃h, L2⦄ ⊢ T2 •*[g] U2 &
+ L1 ⊢ U1 ▶* [d, e] U2.
+/3 width=3/ qed.