In types.xsd:
<xs:simpleType name="Sizes"> <xs:restriction base="xs:postiveIntegers"/> </xs:simpleType> <xs:element name="size" type="my:Sizes"/>
The redefine:
<xs:redefine schemaLocation="types.xsd"> <xs:simpleType name="Sizes"> <xs:restriction base="my:Sizes"> <xs:enumeration value="2"/> <xs:enumeration value="4"/> <xs:enumeration value="6"/> <xs:enumeration value="8"/> <xs:enumeration value="10"/> <xs:enumeration value="12"/> </xs:restriction> </xs:simpleType> </xs:redefine>
The effect is the element 'size' can only have content of '2', '4',...,'12'.