情况1
格式良好的 XML 文档:
<!DOCTYPE root SYSTEM "idtest.dtd">
<root>
<book id="ID01" />
<magazine id="ID01" />
</root>
DTD:
<!ELEMENT root ANY>
<!ELEMENT book ANY>
<!ATTLIST book id ID #IMPLIED>
<!ELEMENT magazine ANY>
<!ATTLIST magazine id ID #IMPLIED>
xmllint 的输出:
$ xmllint --postvalid idtest.xml
<?xml version="1.0"?>
<!DOCTYPE root SYSTEM "idtest.dtd">
<root>
<book id="ID01"/>
<magazine id="ID01"/>
</root>
idtest.xml:4: element magazine: validity error : ID ID01 already defined
<magazine id="ID01" />
^
idtest.xml:4: element magazine: validity error : ID ID01 already defined
Document idtest.xml does not validate
案例2
格式良好的 XML 文档:
<!DOCTYPE root SYSTEM "idtest.dtd">
<root>
<book book_id="ID01" />
<magazine magazine_id="ID01" />
</root>
DTD:
<!ELEMENT root ANY>
<!ELEMENT book ANY>
<!ATTLIST book book_id ID #IMPLIED>
<!ELEMENT magazine ANY>
<!ATTLIST magazine magazine_id ID #IMPLIED>
xmllint 的输出:
$ xmllint --postvalid idtest.xml
<?xml version="1.0"?>
<!DOCTYPE root SYSTEM "idtest.dtd">
<root>
<book book_id="ID01"/>
<magazine magazine_id="ID01"/>
</root>
idtest.xml:4: element magazine: validity error : ID ID01 already defined
<magazine magazine_id="ID01" />
^
idtest.xml:4: element magazine: validity error : ID ID01 already defined
Document idtest.xml does not validate
结论:更改属性名称没有帮助。类型很重要。ID 类型的属性值必须是唯一的。解释1是正确的。