--- /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/static/aaa_aaa.ma".
+include "basic_2/static/lsuba_ldrop.ma".
+
+(* LOCAL ENVIRONMENT REFINEMENT FOR ATOMIC ARITY ASSIGNMENT *****************)
+
+(* Properties concerning atomic arity assignment ****************************)
+
+lemma lsuba_aaa_conf: ∀L1,V,A. L1 ⊢ V ⁝ A → ∀L2. L1 ⁝⊑ L2 → L2 ⊢ V ⁝ A.
+#L1 #V #A #H elim H -L1 -V -A
+[ //
+| #I #L1 #K1 #V1 #B #i #HLK1 #HV1B #IHV1 #L2 #HL12
+ elim (lsuba_ldrop_O1_conf … HL12 … HLK1) -L1 #X #H #HLK2
+ elim (lsuba_inv_pair1 … H) -H * #K2
+ [ #HK12 #H destruct /3 width=5/
+ | #V2 #A1 #HV1A1 #HV2 #_ #H1 #H2 destruct
+ >(aaa_mono … HV1B … HV1A1) -B -HV1A1 /2 width=5/
+ ]
+| /4 width=2/
+| /4 width=1/
+| /3 width=3/
+| /3 width=1/
+]
+qed.
+
+lemma lsuba_aaa_trans: ∀L2,V,A. L2 ⊢ V ⁝ A → ∀L1. L1 ⁝⊑ L2 → L1 ⊢ V ⁝ A.
+#L2 #V #A #H elim H -L2 -V -A
+[ //
+| #I #L2 #K2 #V2 #B #i #HLK2 #HV2B #IHV2 #L1 #HL12
+ elim (lsuba_ldrop_O1_trans … HL12 … HLK2) -L2 #X #H #HLK1
+ elim (lsuba_inv_pair2 … H) -H * #K1
+ [ #HK12 #H destruct /3 width=5/
+ | #V1 #A1 #HV1 #HV2A1 #_ #H1 #H2 destruct
+ >(aaa_mono … HV2B … HV2A1) -B -HV2A1 /2 width=5/
+ ]
+| /4 width=2/
+| /4 width=1/
+| /3 width=3/
+| /3 width=1/
+]
+qed.