reltype

<xs:attribute name="reltype">
  <xs:simpleType>
    <xs:restriction base="xs:NMTOKEN">
      <xs:enumeration value="origination"/>
      <xs:enumeration value="destruction"/>
      <xs:enumeration value="control"/>
      <xs:enumeration value="causa"/>
      <xs:enumeration value="subject"/>
      <xs:enumeration value="other"/>
    </xs:restriction>
  </xs:simpleType>
</xs:attribute>