Re: [xml-dev] What characters can go into a CDATA section and acomment? (I found inconsistencies)
Hi all,
I personally see, few similarities between purposes of CDATA section and a comment within the context of XML documents.
I seem to clearly, understand the purpose of comments. Any text within comments, are only for human reading (and rarely for automated reading by computers. for e.g, we have XPath comment nodes).
But I'd like to know, what are the use cases of CDATA sections. Any thoughts, shall be helpful to know.
Hi Folks,
I did some testing to see what characters can go into a CDATA section and a comment. Here's what I found:
Recall the CDATA syntax: <![CDATA[ ... ]]>
Question: Can the content of a CDATA section contain the ] character?
<![CDATA[foo]bar]]>
Answer: Yes
Question: Can the content of a CDATA section contain ]]?
<test><![CDATA[foo]]bar]]></test>
Answer: Yes.
Question: Can the content of a CDATA section contain more than two ] characters at the end?
<![CDATA[foo]]]]]>
Answer: Yes.
Question: Can the content of a CDATA section contain more than one [ character at the start?
<![CDATA[[[foo]]>
Answer: Yes.
Recall the comment syntax: <!-- ... -->
Question: Can the content of a comment contain a dash character?
<!-- foo - bar -->
Answer: Yes.
Question: Can the content of a comment contain two dashes?
<!-- foo -- bar -->
Answer: No.
Question: Can the content of a comment end with more than two dashes?
<!-- foo----->
Answer: No.
Notice the inconsistency: A CDATA section can end with more than two ] characters but a comment cannot end with more than two dashes:
<![CDATA[foo]]]]]> Okay
<!-- foo-----> Error
Also, a CDATA section can contain ]] but a comment cannot contain --
<![CDATA[foo]]bar]]>
<!-- foo -- bar -->
Why is there this inconsistency?
Isn't inconsistency in a data format language bad?
/Roger
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