
      Edit groups may have a length of 0 and function as tabstops where there
      is no default text, for example, an edit that inserts an <tt>if</tt>
      statement might provide an empty group between parens where a condition
      should be typed. For this reason, it's also valid for a group to contain
      only a single position that is not linked to others.
    </p>
    <object>
      <field name="positions">
        <list>
          <ref>Position</ref>
        </list>
        <p>
          The po