老师请看下我的代码完成的怎样？

<?xml version="1.0" encoding="UTF-8"?>

<teaching-plan xmlns="http://www.w3school.com.cn"
               xmlns:xis="http://www.w3.org/2001/XMLSchema-instance"
               xis:schemaLocation="teaching.xsd">
    <course id="c1">
        <course-name>大学英语</course-name>
        <class-hour>36</class-hour>
        <exam-form>考试</exam-form>
    </course>
    <course id="c2">
        <course-name>高等数学</course-name>
        <class-hour>70</class-hour>
        <exam-form>考试</exam-form>
    </course>
    <course id="c3">
        <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" ?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           targetNamespace="http://www.w3school.com.cn"
           xmlns="http://www.w3school.com.cn"
           elementFormDefault="qualified">
    <xs:element name="teaching-plan">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="course" minOccurs="1" maxOccurs="100" >
                    <xs:complexType>
                        <xs:sequence>
                            <xs:element name="course-name" type="xs:string"></xs:element>
                            <xs:element name="class-hour" >
                                <xs:simpleType>
                                    <xs:restriction base="xs:integer">
                                        <xs:minInclusive value="20"></xs:minInclusive>
                                        <xs:maxInclusive value="110"></xs:maxInclusive>
                                    </xs:restriction>
                                </xs:simpleType>
                            </xs:element>
                            <xs:element name="exam-form" type="xs:string"></xs:element>
                        </xs:sequence>
                        <xs:attribute name="id" type="xs:string" use="required"></xs:attribute>
                    </xs:complexType>
                </xs:element>
            </xs:sequence>
        </xs:complexType>
    </xs:element>







</xs:schema>

我是在idea下编写的代码

我想问一下老师，为什么在idea下编写xsd时每个语句前面都要加xs呢？