value

<xs:attribute name="value" use="required">
  <xs:simpleType>
    <xs:restriction base="xs:token">
      <xs:enumeration value="created"/>
      <xs:enumeration value="revised"/>
      <xs:enumeration value="deleted"/>
      <xs:enumeration value="cancelled"/>
      <xs:enumeration value="derived"/>
      <xs:enumeration value="updated"/>
      <xs:enumeration value="unknown"/>
    </xs:restriction>
  </xs:simpleType>
</xs:attribute>