怎样写XSD文件7<restriction><enumeration>

<hello allFramSize="46/55/60或者small/medium/large">
<welcome>string</welcome>
</hello>


<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:attribute name="allFrameSize">
<xs:simpleType>
<xs:union memberTypes="roadbikeSize mountainbikeSize" />
</xs:simpleType>
</xs:attribute>
<xs:simpleType name="roadbikeSize">
<xs:restriction base="xs:positiveInteger">
<xs:enumeration value="46"/>
<xs:enumeration value="55"/>
<xs:enumeration value="60"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="mountainbikeSize">
<xs:restriction base="xs:string">
<xs:enumeration value="small"/>
<xs:enumeration value="medium"/>
<xs:enumeration value="large"/>
</xs:restriction>
</xs:simpleType>
<xs:element name="hello">
<xs:complexType>
<xs:sequence>
<xs:element name="welcome" type="xs:string"/>
</xs:sequence>
<xs:attribute ref="allFrameSize" use="required" />
</xs:complexType>
</xs:element>
</xs:schema>