--- /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/computation/csn_aaa.ma".
+include "basic_2/computation/xprs_aaa.ma".
+include "basic_2/computation/xprs_cprs.ma".
+include "basic_2/equivalence/cpcs_aaa.ma".
+include "basic_2/dynamic/snv.ma".
+
+(* STRATIFIED NATIVE VALIDITY FOR TERMS *************************************)
+
+(* Properties on atomic arity assignment for terms **************************)
+
+lemma snv_aaa: ∀h,g,L,T. ⦃h, L⦄ ⊩ T :[g] → ∃A. L ⊢ T ⁝ A.
+#h #g #L #T #H elim H -L -T
+[ /2 width=2/
+| #I #L #K #V #i #HLK #_ * /3 width=6/
+| #a * #L #V #T #_ #_ * #B #HV * #A #HA /3 width=2/
+| #a #L #V #W #W0 #T #U #l #_ #_ #HVW #HW0 #HTU * #B #HV * #X #HT
+ lapply (xprs_aaa h g … HV W0 ?) [ /3 width=3/ ] -W #HW0
+ lapply (xprs_aaa … HT … HTU) -HTU #H
+ elim (aaa_inv_abst … H) -H #B0 #A #H1 #HU #H2 destruct
+ lapply (aaa_mono … H1 … HW0) -W0 #H destruct /3 width=4/
+| #L #W #T #U #l #_ #_ #HTU #HUW * #B #HW * #A #HT
+ lapply (aaa_cpcs_mono … HUW A … HW) -HUW /2 width=7/ -HTU #H destruct /3 width=3/
+]
+qed-.
+
+lemma snv_csn: ∀h,g,L,T. ⦃h, L⦄ ⊩ T :[g] → L ⊢ ⬊* T.
+#h #g #L #T #H elim (snv_aaa … H) -H /2 width=2/
+qed-.