hecks if there are rules
    for any relation. When processing the range table entry for
    <TT
CLASS="LITERAL"
>shoelace</TT
> (the only one up to now) it finds the
    <TT
CLASS="LITERAL"
>_RETURN</TT
> rule with the query tree:

</P><PRE
CLASS="PROGRAMLISTING"
>SELECT s.sl_name, s.sl_avail,
       s.sl_color, s.sl_len, s.sl_unit,
       s.sl_len * u.un_fact AS sl_len_cm
  FROM shoelace old, shoelace new,
       shoelace_data s, unit u
 WHERE s.sl_unit = u.un_name;</PRE
><P></P
><P
>    To expand the vie