<simpleType name="TimeUnitType">
  <union>
    <simpleType>
      <restriction base="string">
        <enumeration value="year"/>
        <enumeration value="month"/>
        <enumeration value="day"/>
        <enumeration value="hour"/>
        <enumeration value="minute"/>
        <enumeration value="second"/>
      </restriction>
    </simpleType>
    <simpleType>
      <restriction base="string">
        <pattern value="other:\w{2,}"/>
      </restriction>
    </simpleType>
  </union>
</simpleType>