/I> ( '|' <I>field</I> )*</TR>
  <TR><TD ALIGN=right>where <I>field</I><TD>=<TD>fieldId</I> or '{' <I>rlabel</I> '}'</TR>
  <TR><TD ALIGN=right>and <I>fieldId</I><TD>=<TD> [ '<' <I>string</I> '>'] [ <I>string</I> ]</TR>
  </TABLE>
Braces, vertical bars and angle brackets must be escaped with
a backslash character if you wish them to appear as a literal character.
Spaces are interpreted as separators between tokens,
so they must be escaped if you want spaces in the text.
<P>
The first string in <I>fieldId</I