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diff --git a/matitaB/components/ng_paramodulation/terms.ml b/matitaB/components/ng_paramodulation/terms.ml
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+(*
+    ||M||  This file is part of HELM, an Hypertextual, Electronic        
+    ||A||  Library of Mathematics, developed at the Computer Science     
+    ||T||  Department, University of Bologna, Italy.                     
+    ||I||                                                                
+    ||T||  HELM is free software; you can redistribute it and/or         
+    ||A||  modify it under the terms of the GNU General Public License   
+    \   /  version 2 or (at your option) any later version.      
+     \ /   This software is distributed as is, NO WARRANTY.     
+      V_______________________________________________________________ *)
+
+(* $Id$ *)
+
+type 'a foterm = 
+  | Leaf of 'a
+  | Var of int
+  | Node of ('a foterm) list
+
+type 'a substitution = (int * 'a foterm) list
+
+type comparison = Lt | Eq | Gt | Incomparable | Invertible
+
+type rule = Superposition | Demodulation
+type direction = Left2Right | Right2Left | Nodir
+type position = int list
+
+type 'a proof =
+  | Exact of 'a foterm
+  | Step of rule * int * int * direction * position * 'a substitution
+         (* rule, eq1, eq2, direction of eq2, position, substitution *)
+
+type 'a literal = 
+ | Equation of    'a foterm  (* lhs *)
+                * 'a foterm  (* rhs *)
+                * 'a foterm  (* type *)
+                * comparison (* orientation *)
+ | Predicate of   'a foterm 
+
+type varlist = int list
+
+type 'a unit_clause =
+   int        (* ID *)
+ * 'a literal
+ * varlist       (* variable list *)
+ * 'a proof      (* proof *)
+
+type 'a passive_clause = int * 'a unit_clause (* weight * equation *)
+
+let is_eq_clause (_,l,_,_) =
+  match l with
+    | Equation _ -> true
+    | Predicate _ -> false
+;;
+
+let vars_of_term t =
+  let rec aux acc = function
+    | Leaf _ -> acc
+    | Var i -> if (List.mem i acc) then acc else i::acc
+    | Node l -> List.fold_left aux acc l
+  in aux [] t
+;;
+
+module OT =
+ struct
+   type t = int 
+   let compare = Pervasives.compare
+ end
+
+module M : Map.S with type key = int 
+  = Map.Make(OT) 
+
+type 'a bag = int
+              * (('a unit_clause * bool * int) M.t)
+
+  let add_to_bag (_,lit,vl,proof) (id,bag) =
+    let id = id+1 in
+    let clause = (id, lit, vl, proof) in
+    let bag = M.add id (clause,false,0) bag in
+    (id,bag), clause 
+   ;;
+
+  let replace_in_bag ((id,_,_,_),_,_ as cl) (max_id,bag) =
+    let bag = M.add id cl bag in
+      (max_id,bag)
+  ;;
+
+  let get_from_bag id (_,bag) =
+    M.find id bag
+  ;;
+    
+  let empty_bag = (0,M.empty);;
+
+module type Blob =
+  sig
+    type t
+    val eq : t -> t -> bool
+    val compare : t -> t -> int
+    val eqP : t
+    val is_eq: t foterm -> (t foterm* t foterm *t foterm) option 
+    val pp : t -> string
+    type input
+    val embed : input -> t foterm
+    val saturate : input -> input -> t foterm * t foterm
+  end
+