引用：
<?xml version="1.0" encoding="UTF-8"?>
<!-- edited with XML Explorer v2.0 by Mergesoft (www.mergesoft.com)-->
<!DOCTYPE DOCUMENT[
    <!ELEMENT COCUMENT (TITLE,SIGNATURE)>
    <!ELEMENT TITLE (#PCDATA)>
    <!ELEMENT COPYRIGHT (#PCDATA)>
    <!ELEMENT EMAIL (#PCDATA)>
    <!ELEMENT SIGNATURE (COPYRIGHT,EMAIL)>
    <!ENTITY abc SYSTEM "qianzi.xml">
]>
  <DOCUMENT>
    <TITLE>xuexue</TITLE>
      &abc;
  </DOCUMENT>
这两个文件是在同一目录下的，那为什么<!ENTITY abc SYSTEM "qianzi.xml">这句还报错啊。难道qianzi.xml还要格式化吗，好郁闷，哪个高人来说说啊。

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--------------------------------------------------------------------------------

External ID is invalid. Error processing resource 'file:///D:/XML/练习/new4.xml'. Line 9, Position 18

    <!ENTITY abc CDATA "qianzi.xml">

<?xml version="1.0" encoding="UTF-8" ?>
- <!--  edited with XML Explorer v2.0 by Mergesoft (www.mergesoft.com)
  -->
  <!DOCTYPE DOCUMENT (View Source for full doctype...)>
- <DOCUMENT>
  <TITLE>xuexue</TITLE>
- <!--  edited with XML Explorer v2.0 by Mergesoft (www.mergesoft.com)
  -->
- <SIGNATURE>
  <COPYRIGHT>1999</COPYRIGHT>
  <EMAIL>xuexue425@yaoo.com.cn</EMAIL>
  </SIGNATURE>
  </DOCUMENT>

qianzi.xml里面只写这些就行了
声明语句不要要，否则就会报错