思科路由器存储分类介绍

DTD（Document Type Definition）文档类型定义可分为三种
a.内部定义
b.外部定义
c.内部和外部定义
1.内部定义student.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE student[
<!ELEMENT student (name,age)>
<!ELEMENT name (#PCDATA)>
<!ELEMENT age (#PCDATA)>
]>

<student>
<name>zs</name>
<age>22</age>
</student>

2.外部定义
student1.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE student SYSTEM "student.dtd">
<student>
<name>zs</name>
<age>22</age>
</student>

student.dtd

<?xml version="1.0" encoding="UTF-8"?>
<!ELEMENT student (name,age)>
<!ELEMENT name (#PCDATA)>
<!ELEMENT age (#PCDATA)>

3.内外部定义
student2.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE student SYSTEM "student.dtd" [
<!ELEMENT student (name,age)>
]>
<student>
<name>zs</name>
<age>22</age>
</student>

student2.dtd

<?xml version="1.0" encoding="UTF-8"?>
<!ELEMENT name (#PCDATA)>
<!ELEMENT age (#PCDATA)>