XHTML 5 and validation

[Jesper Tverskov <jesper.tverskov@gmail.com>]

XHTML 5 and validation

Since around 2005 I have served my webpages as XHTML 1.1 with mimetype
"application/xhtml+xml" to the browsers understanding it and as XHTML
1.0 with mimetype "text/html" to the rest. The last couple of days I
have tested if something similar is possible with XHTML 5.

"HTML5" is supposed to come in an HTML and an XHTML version. I have a
feeling that at least the XML community would like to use the XHTML
version, either XHTML 5 served with mimetype "application/xhtml+xml"
to the browsers understanding it, or as a minimum well-formed HTML5
looking like XHTML served with "text/html".

The problem is that we are allowed to use well-formed HTML5, and we
are allowed to use lower-case for element and attribute names, but we
cannot validate it with e.g. W3C's HTML Validator. In HTML5 an "img"
element is allowed to be spelled "img", "IMG", "iMg", ImG", etc., in
one and the same document.

Even worse, XHTML5 has exactly the same DOCTYPE as HTML5. To get the
document validated as XHTML5 you must serve it to the validator with
"application/xhtml+xml". To do that you cannot just upload it but you
must serve it with a webserver and fine tune it to use an XML
mimetype, or you must set the mimetype with server-side scripting just
to get a document validated!

Excuse me, but what I have just described, is enough to conclude that
it is very unlikely that XHTML5 will get any traction what so ever. It
is too difficult to use. Unless the XML community does something to
make it easier to validate XHTML5 and make it possible to validate
well-formed, "XHTML style", HTML5.

Cheers,
Jesper Tverskov
http://www.xmlplease.com