<simpleType name="PropertyDataTypeEnumType">
  <union memberTypes="diggs:DataTypeEnumType">
    <simpleType>
      <restriction base="string">
        <enumeration value="">
          <annotation>
            <documentation>The empty string: the data type of the property is not stated (an unknown type).</documentation>
          </annotation>
        </enumeration>
      </restriction>
    </simpleType>
  </union>
</simpleType>