<?xml version="1.0" encoding='UTF-8'?>
<!DOCTYPE Letter [
<!ELEMENT Letter (to, from, Title, Text) >
<!ATTLIST Letter date CDATA #REQUIRED >
<!ELEMENT to (#PCDATA) >
<!ELEMENT from (#PCDATA) >
<!ELEMENT Title (#PCDATA) >
<!ELEMENT Text (#PCDATA) >
]>
<Letter date="2006-04-17">
   <to>学生</to>
   <from>Martin</from>
   <Title>念のため</Title>
   <Text>宿題を忘れないでください。</Text>
</Letter>