XML文件外部写法--引入DTD规范

pet.dtd

<!ELEMENT pets (dogs,penguins)>
<!ELEMENT dogs (dog*)>
<!ATTLIST dog id CDATA #REQUIRED>
<!ELEMENT dog (health,love,decHealth,incLove)>
<!ELEMENT penguins (penguin*)>
<!ATTLIST penguin id CDATA #REQUIRED>
<!ELEMENT penguin (health,love,decHealth,incLove)>
<!ELEMENT health (#PCDATA)>
<!ELEMENT love (#PCDATA)>
<!ELEMENT decHealth (#PCDATA)>
<!ELEMENT inclove (#PCDATA)>

XML.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE pets SYSTEM "pet.dtd" >
<pet>
  <dogs>
	  <dog id="1">
		<health>100</health>
		<love>0</love>
		<decHealth>18</decHealth>
		<incLove>10</incLove>
	  </dog>
  </dogs>
	<dogs>
	  <dog id="2">
		<health>100</health>
		<love>0</love>
		<decHealth>18</decHealth>
		<incLove>10</incLove>
	  </dog>
	</dogs>
	<dogs>
	  <dog id="3">
		<health>100</health>
		<love>0</love>
		<decHealth>28</decHealth>
		<incLove>30</incLove>
	  </dog>
	</dogs>
	<penguins>
	  <penguin id="4">
		<health>100</health>
		<love>0</love>
		<decHealth>15</decHealth>
		<incLove>8</incLove>
	  </penguin>
	</penguins>
</pet>