一个简单的基于XML的模块集成框架(2)

<?xml version="1.0" encoding="UTF-8"?>
<!-- edited with XMLSpy v2006 sp2 U (http://www.altova.com) by peter (hust) -->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
    <xs:element name="Menu">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="MenuItem" maxOccurs="unbounded"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:element name="MenuItem">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="MenuItem" minOccurs="0" maxOccurs="unbounded"/>
            </xs:sequence>
            <xs:attribute name="AddToolButton">
                <xs:simpleType>
                    <xs:restriction base="xs:string">
                   &