unit:TimeUnitType

<xsd:simpleType name="TimeUnitType">
  <xsd:restriction base="xsd:string">
    <xsd:enumeration value="sec"/>
    <!-- second -->
    <xsd:enumeration value="min"/>
    <!-- minute -->
    <xsd:enumeration value="hr"/>
    <!-- hour -->
    <xsd:enumeration value="day"/>
    <xsd:enumeration value="week"/>
    <xsd:enumeration value="month"/>
    <xsd:enumeration value="year"/>
  </xsd:restriction>
</xsd:simpleType>