是& gt;有必要吗 [英] Is > ever necessary?

问题描述

自从7年以来我现在开发网站和XML界面，从来没有遇到过需要使用& gt; 的情况> 。所有的歧义都可以通过引用 ，& ， code>和'单独。

有没有人曾经遇到过一个情况（例如， SGML处理，浏览器问题，XSLT，...）你发现它不可避免地用& gt; ？

更新：我刚检查过 XML规范< a>，例如，关于第2.4节中的字符数据：

字符数据

  [14] CharData :: = [^&] *']]>'[^< &] *）
  

所以即使在那里，> 不被提及作为特殊的东西，除了从CDATA部分的结束顺序。

这一个单一的情况，其中> 有任何意义，将是CDATA部分的结尾，]]> ，但是再一次，如果你引用它，引用（即文字字符串] ]& gt; ）将直接在输出中（因为它是 ）。

解决方案

你不需要绝对的，因为几乎任何XML解释器都会明白你的意思。但是如果你这样做，你仍然使用一个没有任何保护的特殊字符。

XML是关于语义的，这并不是真正符合语义的。
$ b

关于您的更新，您忘记了这一部分：

直角括号（>）可以使用字符串>来表示，并且为了兼容，必须使用& gt; 或字符引用转义出现在字符串]]> 内容中，当该字符串未标记CDATA节的结尾。

文档中给出的用例更多的是这样的：

  < XmlMarkup中> 
]]> 
< / xmlmarkup> 
  

这里]]> 对于旧的SGML解析器来说，这是一个问题，因此必须必须转义为= ]]& gt; b $ b

I now develop websites and XML interfaces since 7 years, and never, ever came in a situation, where it was really necessary to use the > for a >. All disambiguition could so far be handled by quoting <, &, " and ' alone.

Has anyone ever been in a situation (related to, e.g., SGML processing, browser issues, XSLT, ...) where you found it indespensable to escape the greater-than sign with >?

Update: I just checked with the XML spec, where it says, for example, about character data in section 2.4:

Character Data

[14]      CharData       ::=      [^<&]* - ([^<&]* ']]>' [^<&]*)

So even there, the > isn't mentioned as something special, except from the ending sequence of a CDATA section.

This one single case, where the > is of any significance, would be the ending of a CDATA section, ]]>, but then again, if you'd quote it, the quote (i.e., the literal string ]]>) would land literally in the output (since it's CDATA).

解决方案

You don't need to absolutely because almost any XML interpreter will understand what you mean. But still you use a special character without any protection if you do so.

XML is all about semantic, and this is not really semantic compliant.

About your update, you forgot this part :

The right angle bracket (>) may be represented using the string " > ", and must, for compatibility, be escaped using either " > " or a character reference when it appears in the string " ]]> " in content, when that string is not marking the end of a CDATA section.

The use case given in the documentation is more about something like this :

<xmlmarkup>
]]>
</xmlmarkup>

Here the ]]> part could be a problem with old SGML parsers, so it must be escaped into = ]]> for compatibilities reasons.

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