xml外部DTD及引用方法

//外部DTD

<!ELEMENT pets (dogs,penguins)>
<!ELEMENT dogs (dog*)>
<!ELEMENT penguins (penguin+)>
<!ELEMENT dog (name,health,love,strain?)>
<!ATTLIST dog id CDATA #REQUIRED>
<!ELEMENT penguin (name,health,love,sex)>
<!ATTLIST penguin id CDATA #REQUIRED>
<!ELEMENT name (#PCDATA)>
<!ELEMENT health (#PCDATA)>
<!ELEMENT love (#PCDATA)>
<!ELEMENT strain (#PCDATA)>
<!ELEMENT sex (#PCDATA)>

<?xml version="1.0" encoding="UTF-8"?>
<!-- 使用CSS样式修饰XML数据 -->

<!-- 使用外部DTD文件 -->
<!DOCTYPE pets SYSTEM "pet.dtd" >
<pets>
<dogs>
  <dog id="1">  
   <name>YAYA</name>
   <health>100</health>
   <love>0</love>
   <strain>酷酷的雪娜瑞</strain>
  </dog>
  <dog id="2">  
   <name>OUOU</name>
   <health>90</health>
   <love>15</love>
   <strain>聪明的拉布拉多犬</strain>
  </dog>
</dogs>
<penguins>
  <penguin id="3">  
   <name>QQ</name>
   <health>100</health>
   <love>20</love>
   <sex>Q仔</sex>  
  </penguin> 
</penguins>
</pets>