xlink:type

<attribute name="type">
  <simpleType>
    <restriction base="string">
      <enumeration value="simple"/>
      <enumeration value="extended"/>
      <enumeration value="locator"/>
      <enumeration value="arc"/>
      <enumeration value="resource"/>
      <enumeration value="title"/>
      <enumeration value="none"/>
    </restriction>
  </simpleType>
</attribute>