--- /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/syntax/term.ma".
+
+(* BINDERS FOR LOCAL ENVIRONMENTS ******************************************)
+
+include "basic_2/syntax/term_weight.ma".
+include "basic_2/syntax/bind.ma".
+
+(* WEIGHT OF A BINDER FOR LOCAL ENVIRONMENTS *******************************)
+
+rec definition bw I ≝ match I with
+[ BUnit _ ⇒ 1
+| BPair _ V ⇒ ♯{V}
+].
+
+interpretation "weight (binder for local environments)" 'Weight I = (bw I).
+
+(* Basic properties *********************************************************)
+
+lemma bw_pos: ∀I. 1 ≤ ♯{I}.
+* //
+qed.