<simpleType name="MaterialEnumType">
  <union>
    <simpleType>
      <restriction base="string">
        <enumeration value="fluid"/>
        <enumeration value="gas"/>
        <enumeration value="oil"/>
        <enumeration value="rock"/>
        <enumeration value="soil"/>
        <enumeration value="water"/>
      </restriction>
    </simpleType>
    <simpleType>
      <restriction base="string">
        <pattern value="Other: .{2,}"/>
      </restriction>
    </simpleType>
  </union>
</simpleType>