+(**************************************************************************)
+(* ___ *)
+(* ||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/rt_computation/cpme_aaa.ma".
+include "basic_2/rt_computation/cpre_cpre.ma".
+include "basic_2/rt_equivalence/cpes.ma".
+include "basic_2/dynamic/cnv_cpme.ma".
+
+(* CONTEXT-SENSITIVE NATIVE VALIDITY FOR TERMS ******************************)
+
+(* Properties with t-bound rt-equivalence for terms *************************)
+
+lemma cnv_cpes_dec (a) (h) (n1) (n2) (G) (L):
+ ∀T1. ⦃G,L⦄ ⊢ T1 ![a,h] → ∀T2. ⦃G,L⦄ ⊢ T2 ![a,h] →
+ Decidable … (⦃G,L⦄ ⊢ T1 ⬌*[h,n1,n2] T2).
+#a #h #n1 #n2 #G #L #T1 #HT1 #T2 #HT2
+elim (cnv_fwd_aaa … HT1) #A1 #HA1
+elim (cnv_fwd_aaa … HT2) #A2 #HA2
+elim (cpme_total_aaa h n1 … HA1) -HA1 #U1 #HTU1
+elim (cpme_total_aaa h n2 … HA2) -HA2 #U2 #HTU2
+elim (eq_term_dec U1 U2) [ #H destruct | #HnU12 ]
+[ cases HTU1 -HTU1 #HTU1 #_
+ cases HTU2 -HTU2 #HTU2 #_
+ /3 width=3 by cpms_div, or_introl/
+| @or_intror * #T0 #HT10 #HT20
+ lapply (cnv_cpme_cpms_conf … HT1 … HT10 … HTU1) -T1 #H1
+ lapply (cnv_cpme_cpms_conf … HT2 … HT20 … HTU2) -T2 #H2
+ /3 width=6 by cpre_mono/
+]
+qed-.