xsd – 使用xs：all扩展XML Schema类型有什么问题？

<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns="http://tempuri.org/ServiceDescription.xsd" xmlns:mstns="http://tempuri.org/ServiceDescription.xsd" xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://tempuri.org/ServiceDescription.xsd" elementFormDefault="qualified" id="ServiceDescription">
    <xs:element name="Template">
        <xs:complexType>
            <xs:complexContent>                                     
                <xs:extension base="ServiceType">
                    <xs:all>
                        <xs:element name="TemplateCode" type="xs:string"/>
                    </xs:all>
                </xs:extension>
            </xs:complexContent>
        </xs:complexType>
    </xs:element>
    <xs:complexType name="ServiceType">
        <xs:all>
            <xs:element name="ServiceCode" type="xs:string"/>
        </xs:all>
    </xs:complexType>
</xs:schema>

当我尝试在XMLSpy中保存它时,它告诉我

An ‘all’ model group is neither allowed in complex type definition ‘mstns:ServiceType’ nor in its extension ‘{anonymous}’.

单击“详细信息”会显示指向a paragraph in XML Schema specification的链接,我不明白.

补充：啊,是的,忘了提 – 错误的行是这一行：

<xs:element name="TemplateCode" type="xs:string"/>