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Re: XHTML2 MIME type

From: Masayasu Ishikawa <mimasa@w3.org>
Date: Wed, 09 Apr 2003 20:22:25 +0900 (JST)
Message-Id: <20030409.202225.74743813.mimasa@w3.org>
To: www-html@w3.org

Jim Dabell <jim-www-html@jimdabell.com> wrote:

> Will there be a new MIME type for XHTML2, or are people expecting to use 
> application/xhtml+xml?

Current WG position is that we'd use 'application/xhtml+xml', with
optional 'profile' parameter to indicate XHTML2, if necessary.
RFC 3236 needs to be updated at some point in which case, but there
are other things to be considered in addition to media types (see below).

> If there is not going to be an XHTML2-specific MIME 
> type, how are servers supposed to distinguish between user-agents that can 
> handle XHTML2 and those that cannot (for the purpose of content negotiation 
> in particular)?

As Mr. Woolley pointed out, RFC 2616 (HTTP/1.1), "14.1 Accept" includes
a detailed explanation about the Accept header, including examples for
using parameters to distinguish variants of the same media type [1].

However, while media type is an important mechanism to identify the type
of resource, it is not always sufficient to describe heterogeneous
resource, such as a "hybrid" XML document which mixes various markup
languages together, and user agent capability to handle such a resource.

It is quite possible that an XHTML2 document might also include MathML,
SVG, RDF and so on, and such a resource could still be served as
'application/xhtml+xml' or 'application/xml', so the media type alone
is not very informative to describe such a resource, nor registering
media types for every possible combination is practical.  Namespaces
are often used for further dispatching an appropriate processor within
an XML resource, and the proposed 'xmlns' media feature tag is an attempt
to identify those namespaces at a protocol level [2].  Yet sometimes
namespaces are not sufficient to determine the desirable processing.

This issue has been discussed at length on www-tag, first as
the TAG issue "nsMediaType-3" [3], which was subsumed by
"mixedNamespaceMeaning-13" [4] and later split into
"mixedUIXMLNamespace-33" [5], "xmlFunctions-34" [6] and
"RDFinXHTML-35" [7].  Those issues are not resolved yet, and the final
resolution of determining an appropriate media type for XHTML2 should
be made in close coordination with those issues.

[1] http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.1
[2] http://www.ietf.org/internet-drafts/draft-stlaurent-feature-xmlns-03.txt
[3] http://www.w3.org/2001/tag/ilist#nsMediaType-3
[4] http://www.w3.org/2001/tag/ilist#mixedNamespaceMeaning-13
[5] http://www.w3.org/2001/tag/ilist#mixedUIXMLNamespace-33
[6] http://www.w3.org/2001/tag/ilist#xmlFunctions-34
[7] http://www.w3.org/2001/tag/ilist#RDFinXHTML-35

Masayasu Ishikawa / mimasa@w3.org
W3C - World Wide Web Consortium
Received on Wednesday, 9 April 2003 07:22:27 UTC

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