针对DTD的XML验证 [英] XML validation against DTD

问题描述

我具有以下XML和嵌入式DTD：

I have this XML along with an embedded DTD:

<?xml version="1.0" ?>
<!DOCTYPE customers [
<!ELEMENT customers (name,age,roll,sex)>
<!ELEMENT name (#CDATA)>
<!ELEMENT age (#CDATA)>
<!ELEMENT roll (#CDATA)>
<!ELEMENT sex (#CDATA)>
]>
<customers>
<name>XYZ</name>
<age>19</age>
<roll>23</roll>
<sex>M</sex>
</customers>

当我尝试验证XML时，它向我显示了一个错误。但是，如果我将#CDATA更改为#PCDATA，则验证成功。

When i try to validate the XML, its showing me an error. But if i change the #CDATA to #PCDATA then the validation is successful.

问题1）我没有适当的解释，为什么会这样。两者之间的唯一区别是：#CDATA将不进行解析，而#PCDATA将进行解析。在这种情况下。两次验证都应该成功吧？请说明我错在哪里，因为此验证的输出与我的概念背道而驰。

Question 1) I don't have a proper explanation why is this happening. The only difference between the two is: #CDATA will not parse whereas #PCDATA will parse. In such a case. both the validations should succeed right? Please explain where am i wrong since the output of this validation is going against my concept.

问候，

推荐答案

在XML DTD中没有像 #CDATA 这样的东西。这是一个未知的关键字。这就是为什么会出现错误。

There is no such thing as #CDATA available for use in XML DTDs. It is an unknown keyword. That's why you get an error.

CDATA 是在声明属性时使用的关键字在DTD中。您不能声明元素的类型为 CDATA （或 #CDATA ）。

CDATA is a keyword that is used when declaring attributes in a DTD. You cannot declare an element to be of type CDATA (or #CDATA).

在CDATA部分中也找到了字符串 CDATA （<！[CDATA [ ...]]> ），这是完全不同的东西。可以在XML文档中使用它们来转义字符（如& ），否则这些字符将被解释为标记。在DTD中未声明CDATA节；

The string CDATA is also found in CDATA sections (<![CDATA[ ... ]]>), which are entirely different things. They can be used in an XML document to escape characters (such as &) that would otherwise be interpreted as markup. CDATA sections are not declared in the DTD; they are simply used when needed.

如果您有标记，例如< name> L& T< / name> （未包含在CDATA部分中），那么它将被解析器拒绝。在DTD中声明 name 元素并不重要。

If you have markup such as <name>L&T</name> (that is not enclosed in a CDATA section), then it will be rejected by the parser. It does not matter how the name element is declared in the DTD.

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