- From: Jukka K. Korpela <jkorpela@cs.tut.fi>
- Date: Sat, 3 Feb 2007 13:22:01 +0200 (EET)
- To: www-validator@w3.org
The occurrence of the less than sign "<" or the ampersand "&" as character
data in an XHTML document causes the W3C Markup Validator to issue a
warning. The document is then reported as valid. For a trivial demo, see
http://validator.w3.org/check?uri=http%3A%2F%2Fwww.cs.tut.fi%2F%7Ejkorpela%2Ftest%2Ftest.xhtml
This is incorrect, since such occurrences are errors by XML rules:
"The ampersand character (&) and the left angle bracket (<) MUST NOT
appear in their literal form, except when used as markup delimiters, or
within a comment, a processing instruction, or a CDATA section. If they
are needed elsewhere, they MUST be escaped using either numeric character
references or the strings "&" and "<" respectively."
http://www.w3.org/TR/REC-xml/#syntax
Note that even the formal syntax in the XML specification excludes
"&" and "<" as data characters:
[14] CharData ::= [^<&]* - ([^<&]* ']]>' [^<&]*)
This means that the data as a whole cannot match the production for
"document", so it does not constitute an XML document at all, i.e. it is
not even "well-formed" (ref.:
http://www.w3.org/TR/REC-xml/#sec-well-formed ).
--
Jukka "Yucca" Korpela, http://www.cs.tut.fi/~jkorpela/
Received on Saturday, 3 February 2007 11:22:21 UTC