xml - 将属性类型声明为 XML 中的实体时出现验证错误

Question

这是我的 DTD 文件。

?xml version="1.0" encoding="UTF-8"?>
<!-- edited with XML Spy v3.0.7 NT (http://www.xmlspy.com) by Manukyan (YSU) -->
<!ENTITY xxx "ccc">
<!ENTITY yyy "ddd">
<!ELEMENT book (author+, title, publisher)>
<!ELEMENT author (#PCDATA)>
<!ELEMENT title (#PCDATA)>
<!ELEMENT publisher (#PCDATA)>
<!ATTLIST title
    aaa ENTITY  #IMPLIED
>

这是相应的 DSD 文件。

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book SYSTEM "C:\Users\PC\Desktop\XML\XMLDB\XML\BOOK.DTD">
<book>
    <author>asd</author>
    <title aaa="xxx"/>
    <publisher/>
</book>

我收到了一个验证错误。 属性“aaa”的值部分“xxx”必须是未解析实体的名称。

Answer 1

如@Daniel Haley explains in his answer对于类似的问题，如果您为 ccc 添加实体声明和符号 (NDATA) 声明，则 XML 现在有效:

<!DOCTYPE book [

<!NOTATION ccc SYSTEM "ccc">
<!ENTITY xxx SYSTEM "ccc" NDATA ccc>

<!ENTITY yyy "ddd">
<!ELEMENT book (author+, title, publisher)>
<!ELEMENT author (#PCDATA)>
<!ELEMENT title (#PCDATA)>
<!ELEMENT publisher (#PCDATA)>
<!ATTLIST title aaa ENTITY  #IMPLIED>
]>
<book>
    <author>asd</author>
    <title aaa="xxx"/>
    <publisher/>
</book>