Element declaring

[=?gb2312?B?s8LF9A==?= <jacky_chenp@ustc.edu>]

hi,

  There is a problem when i am writing an xml schema.

      <xs:element name="begintime" default="03-01">
        <xs:simpleType>
         <xs:restriction base="xs:string">
          <xs:pattern value="\d{2}-\d{2}"/>
          <xs:enumeration value="03-01"/>
          <xs:enumeration value="07-01"/>
         </xs:restriction>
        </xs:simpleType>
       </xs:element>

Usually, there are two values for "begintime".But some times(very few) there maybe other values such as "04-01"... According to the definition of xs:enumeration, I can only use the value which is in the list.

 

How to declare the element "begintime" in the best way?thanks

     Best Regards.
       jacky  Keenmicro