diff --git a/C/exo_udi.c b/C/exo_udi.c
index d03c2737c..7aa59588b 100644
--- a/C/exo_udi.c
+++ b/C/exo_udi.c
@@ -170,6 +170,34 @@ Interval(struct index_t *it, Term min, Term max, Term op, BITS32 off USES_REGS)
      pt  = c+(it->links[off]+1);
      end  = c+(it->links[off]+n);
    } else {
+     if (!IsVarTerm(min)) {
+       Int x;
+       if (!IsIntegerTerm(min)) {
+	 min = Yap_Eval(min);
+	 if (!IsIntegerTerm(min)) {
+	   Yap_Error(TYPE_ERROR_INTEGER, min, "data-base constraint");
+	   return FAILCODE;
+	 }
+       }
+       x = IntegerOfTerm(min);
+       if (x >= IntegerOfTerm(S[LOCAL_exo_arg])) {
+	 return FAILCODE;
+       }     
+     }
+     if (!IsVarTerm(max)) {
+       Int x;
+       if (!IsIntegerTerm(max)) {
+	 max = Yap_Eval(max);
+	 if (!IsIntegerTerm(max)) {
+	   Yap_Error(TYPE_ERROR_INTEGER, max, "data-base constraint");
+	   return FAILCODE;
+	 }
+       }
+       x = IntegerOfTerm(max);
+       if (x <= IntegerOfTerm(S[LOCAL_exo_arg])) {
+	 return FAILCODE;
+       }     
+     }
      return NEXTOP(NEXTOP(it->code,lp),lp);
    }
 
diff --git a/library/exo_interval.yap b/library/exo_interval.yap
index a625386aa..dc391118c 100644
--- a/library/exo_interval.yap
+++ b/library/exo_interval.yap
@@ -9,7 +9,10 @@
 :- module(exo_interval,
 	[max/2,
 	 min/2,
+	 max/1,
+	 min/1,
 	 any/2,
+	 any/1,
 	 max/3,
 	 min/3,
 	 any/3,
@@ -40,6 +43,15 @@ max(X, X) :-
 min(X, X) :-
 	insert_atts(X, i(_,_,min)).
 
+max(X) :-
+	insert_atts(X, i(_,_,max)).
+
+any(X) :-
+	insert_atts(X, i(_,_,any)).
+
+min(X) :-
+	insert_atts(X, i(_,_,min)).
+
 
 X #> Y :-
 	( var(X) -> insert_atts(X, i(Y,_,_))
@@ -55,49 +67,24 @@ X #> Y :-
 
 X #>= Y :-
 	( var(X) -> insert_atts(X, i(Y-1,_,_))
-                  ;
-	          ( var(Y) -> insert_atts(Y, i(X+1,_,_) ) ; 
-		      true
-		  )
-	      ;
-          var(Y) -> insert_atts(Y, i(_,X+1,_))
         ;
 	  X >= Y
         ).
 
 X #< Y :-
 	( var(X) -> insert_atts(X, i(_,Y,_))
-                  ;
-	          ( var(Y) -> insert_atts(Y, i(X,_,_) ) ; 
-		      true
-		  )
-	      ;
-	  var(Y) -> insert_atts(Y, i(X,_,_))
         ;
 	  X < Y
         ).
 
 X #=< Y :-
 	( var(X) -> insert_atts(X, i(Y+1,_,_))
-                  ;
-	          ( var(Y) -> insert_atts(Y, i(X-1,_,_) ) ; 
-		      true
-		  )
-	      ;
-          var(Y) -> insert_atts(Y, i(X-1,_,_))
         ;
 	  X =< Y
         ).
 
 X #= Y :-
-	( var(X) -> insert_atts(X, i(Y-1,Y+1,_))
-                  ;
-	          ( var(Y) -> insert_atts(Y, i(X-1,X+1,_) ) ; 
-		      true
-		  )
-	      ;
-          var(Y) -> insert_atts(Y, i(X-1,X+Y,_))
-        ;
+	( var(X) -> insert_atts(X, i(Y-1,Y+1,_)) ;
 	  X =:= Y
         ).
 
@@ -173,5 +160,5 @@ expand_op(A1, A2, A3) :-
 	 A1 == min, A2 = max -> A3 = unique;
 	 A1 == min -> A3 = min;	 A2 == min -> A3 = min;
 	 A1 == max -> A3 = max;	 A2 == max -> A3 = max;
-	 A3 = single
+	 A3 = any
         ).