dtd 属性 枚举类型

<?xml version="1.0" encoding="utf-8"?>

<!DOCTYPE shopping [
	<!ELEMENT book (name,price,count,instock)>
	<!ELEMENT name (#PCDATA)>
	<!ELEMENT price (#PCDATA)>
	<!ELEMENT count (#PCDATA)>
	<!ELEMENT instock (#PCDATA)>
	
	<!--	
		instock标签的
		state属性 枚举类型(y或者n) 必须存在
	-->
	<!ATTLIST instock 
		state (y|n) #REQUIRED
	>
	
]>

<shopping>

	<book>
		<name>抱朴子</name>
		<price>100</price>
		<count>3</count>
		<instock state="y"></instock>					
	</book>

	<book>
		<name>三字经</name>
		<price>200</price>
		<count>5</count>
		<instock state="n"></instock>
	</book>

	<book>
		<name>心经</name>
		<price>300</price>
		<count>7</count>
		<instock state="l"></instock>		
	</book>
	
</shopping>