2.5.1.2 versionType

The versionType specifies a string representing a version number. The version number has one of the following formats: "X.Y", "X.Y.Z", or "X.Y.Z.W", where X, Y, Z, and W contain one or more decimal digits.

 <xs:simpleType name="versionType">
   <xs:restriction base="xs:string">
     <xs:pattern value="\d+(\.\d+){1,3}"/>
   </xs:restriction>
 </xs:simpleType>