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Re: Recognizing xhtml under text/html

From: Henri Sivonen <henris@clinet.fi>
Date: Tue, 11 Dec 2001 20:00:31 +0200
Message-Id: <l03110700b83bed474f2e@[213.243.143.164]>
To: www-html@w3.org
William F. Hammond wrote:

>There is a serious roadblock for the use of MathML in web pages
>arising from the differing expectation of user agents in regard to
>the HTTP content-type for a web page with such content.

Which user agents have which expectations?

MathML-enabled Mozilla builds support XHTML + MathML as text/xml,
application/xml and application/xhtml+xml. Amaya supports XHTML + MathML as
text/xml and application/xhtml+xml.

>For the MathML situation a content provider may use:
>
>    Content-Type: text/html; profile=math
>
>which means:
>
>    The object should be handled as HTML extended by MathML using
>    the best means, if any, the user agent provides,

How would HTML extended by MathML be parsed? XMLness is supposed to lead
away from tag soup. I'm afraid mixing MathML with text/html soup would make
things worse.

>    while other
>    user agents should be sane handling the content classically
>    (though some meaning of content in name space extensions may
>    be lost).

I don't think it makes sense to serve MathML content to old text/html user
agents, because MathML doesn't degrade gracefully. It would make more sense
to serve HTML plus math as images to old text/html user agents.

>Without regard to the particular situation in MathML a content
>provider who wishes to migrate from HTML to fully functioning XHTML
>without providing dual resources and without "throwing a switch" may
>use:
>
>    Content-Type: text/html; profile=xhtml
>
>which means:
>
>    The object should be handled as fully functional XHTML by those
>    user agents prepared to deal with XHTML while older agents
>    should be sane handling it classically.

With Mozilla and old non-math browsers, this effect can already be achieved
using Accept header-based content negotiation to decide between
application/xhtml+xml (or text/xml) and text/html on the server side.

>Appendix C of XHTML 1.0 is relevant for all XHTML, not just 1.0, if a
>content provider wishes new content to be maximally useful in older
>user agents.

Why would MathML and SVG content be useful at all in an old user agent? The
way I understood appendix C was that it applies only to XHTML 1.0 because
XHTML 1.0 doesn't have new elements beyond those that already exist HTML
4.x.

--
Henri Sivonen
henris@clinet.fi
http://www.hut.fi/u/hsivonen/
Received on Tuesday, 11 December 2001 13:01:43 GMT

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