<xs:attribute name="id" type="xs:ID">
  <xs:annotation>
    <xs:appinfo>
      <mdr:definition>A handle for the object. It is of XML type "ID," so is constrained to be unique in the XML document within which it occurs. An external identifier for the object in the form of a URI may be constructed using standard XML and XPointer methods. This is done by concatenating the URI for the document, a fragment separator "#," and the value of the id attribute.</mdr:definition>
    </xs:appinfo>
  </xs:annotation>
</xs:attribute>