Smart Translations:

  In some cases Mach SIx can translate a non-indexed expression into one
  that can be optimized.  The table below shows exactly when a smart
  translation could be used to optimize what would seem to be a non-indexed
  expression.  The first column shows the expression as it would appear in
  the FOR condition.  The second column lists the possible index keys that
  could be used to optimize the first expression.  As long as you have an
  index built on the translation (the second column), the expression in the
  first column is optimizable.  One final note,  Mach SIx will only
  translate keys listed to the left of the relational operator.

                                Optimized using
      Expression                index key
      -----------               ---------------

      empty( Last )             Last

      year( Date )              dtos( Date )
                                Date

      Last = "HEW"              upper( Last )