          The offset of the region from which the user can navigate.
        </p>
      </field>
      <field name="length">
        <ref>int</ref>
        <p>
          The length of the region from which the user can navigate.
        </p>
      </field>
      <field name="targets">
        <list>
          <ref>int</ref>
        </list>
        <p>
          The indexes of the targets (in the enclosing navigation response) to
          which the given region is bound. By opening the target, clients can
 