<simpleType name="NullEnumeration">
  <annotation>
    <documentation>Some common reasons for a null value: innapplicable - the object does not have a value missing - The correct value is not readily available to the sender of this data. Furthermore, a correct value may not exist. template - the value will be available later unknown - The correct value is not known to, and not computable by, the sender of this data. However, a correct value probably exists. withheld - the value is not divulged other:reason - as indicated by "reason" string Specific communities may agree to assign more strict semantics when these terms are used in a particular context.</documentation>
  </annotation>
  <union>
    <simpleType>
      <restriction base="string">
        <enumeration value="inapplicable"/>
        <enumeration value="missing"/>
        <enumeration value="template"/>
        <enumeration value="unknown"/>
        <enumeration value="withheld"/>
      </restriction>
    </simpleType>
    <simpleType>
      <restriction base="string">
        <pattern value="other:\w{2,}"/>
      </restriction>
    </simpleType>
  </union>
</simpleType>