<xs:simpleType name="pressureType">
  <xs:annotation>
    <xs:documentation>The pressure units (can be mmhg, hpa, inhg, mbar)</xs:documentation>
  </xs:annotation>
  <xs:restriction base="xs:NMTOKEN">
    <xs:enumeration value="mmhg"/>
    <xs:enumeration value="hpa"/>
    <xs:enumeration value="inhg"/>
    <xs:enumeration value="mbar"/>
  </xs:restriction>
</xs:simpleType>