老师你看下我这为什么不报错？我是按照你写的和文档上面说的！定义子节点的时候我改来改去就是不报错！

<!--hr.dtd-->

<?xml version="1.0" encoding="UTF-8"?>
<!ELEMENT hr (employee +)>
<!ELEMENT employee (name,age,salary,department)>

<!--hr.xml-->

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hr SYSTEM "hr.dtd">
<!--人力资源管理系统-->
<hr>
 <employee no=3301>
  <name>张二</name>
  <age1>31</age1>
  <salary>4000</salary>
  <department>
   <dname>设计部</dname>
   <address>XX大厦</address>
  </department>
 </employee>
 <employee no=3302>
  <name>张三</name>
  <age1>11</age1>
  <salary>3500</salary>
  <department>
   <dname>统计部</dname>
   <address>XX大厦</address>
  </department>
 </employee>
 <employee no=3303>
  <name>张四</name>
  <age1>21</age1>
  <salary>3000</salary>
  <department>
   <dname>会计部</dname>
   <address>XX大厦</address>
  </department>
 </employee>
</hr>