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>