老师 我这错误在哪呀 一直没找到为啥会错

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE teaching-plan SYSTEM "hr.dtd">
<teaching-plan xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:noNamespaceSchemaLocation="hr.xsd" >
	<course id="abc1">
		<course-name>大学英语</course-name>
		<class-hour>36</class-hour>
		<exam-form>考试</exam-form>
	</course>
	<course id="abc2">
		<course-name>高等数学</course-name>
		<class-hour>70</class-hour>
		<exam-form>考试</exam-form>
	</course>
	<course id="abc3">
		<course-name>计算机应用基础</course-name>
		<class-hour>108</class-hour>
		<exam-form>上机考试</exam-form>
	</course>
</teaching-plan>

<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema">
	<element name="teaching-plan">
		<complexType>
			<sequence>
				<element name="course" minOccurs="1" maxOccurs="100">
					<complexType>
						<sequence>
							<element name="course-name" type="string"></element>
							<element name="class-hour" >
								<simpleType>
									<restriction base="integer">
										<minInclusive value="20"></minInclusive>
										<maxInclusive value="110"></maxInclusive>
									</restriction>
								</simpleType>
							</element>
							<element name="exam-form"  type="string"></element>
						</sequence>
						<attribute name="id" type="string" use="required"></attribute>
					</complexType>
				</element>
			</sequence>
		</complexType>
	</element>
</schema>