private Comparable getLeftDescendingIndexedValue(LeftTuple leftTuple) {
   return (Comparable)
       descendingIndex
           .getDeclaration()
           .getExtractor()
           .getValue(leftTuple.get(descendingIndex.getDeclaration()).getObject());
 }
 private Comparable getRightIndexedValue(RightTuple rightTuple) {
   return (Comparable)
       ascendingIndex.getExtractor().getValue(rightTuple.getFactHandle().getObject());
 }