W3C home > Mailing lists > Public > www-tag@w3.org > January 2003

RE: Value of content negotiation? [was RE: content negotiation anti-principle]

From: <Patrick.Stickler@nokia.com>
Date: Fri, 10 Jan 2003 11:15:20 +0200
Message-ID: <A03E60B17132A84F9B4BB5EEDE57957B5FBAC1@trebe006.europe.nokia.com>
To: <simonstl@simonstl.com>, <www-tag@w3.org>

> On Thursday 09 January 2003 07:59 am, Elliotte Rusty Harold wrote:
> > Just throwing something out: Would it be A. Useful? and B. possible?
> > to add  additional attributes to linking elements to 
> specify the MIME
> > type required? e.g.
> >
> > <a href="foo/" type="text/plain">foo</a>
> > <img src="http://maps.yahoo.com/map?zip=10003" 
> type="image/svg+xml" />
> >
> > and  perhaps for language as well:
> >
> > <a href="foo/" type="text/plain" lang="en-US; en-CA; en-GB; 
> > fr-FR">foo</a>

This approach defeats the purpose of content negotiation, which is
based on contextual issues outside the scope of the link itself,
and unknown by the author. I.e., if your browser supports SVG,
you get an SVG image. If it supports only GIF, you get GIF, etc.
and such knowledge cannot be known before hand and varies
from client to client.

In fact, the same user can view the same document from different
clients (e.g. desktop vs. mobile) and get different variants
at different times. That's what content negotiation is all 

In our systems, we use URNs that do not specify encodings,
language, coverage, revision, etc. and dynamically resolve 
such information at run time based on system and user properties
in order to resolve a link to an actual resource. The link
identifies the body of information, irrespective of form
of expression, and the actual realization is selected at
run time. This also allows new realizations to be added
without modification to the existing links, providing for
live updates and extensions of the information base.

(If someone *wants* to specify the precise encoding, language,
revision, etc. they can, but it makes the link fragile)

Putting the "required" MIME type in the link is simply making
the links that much more fragile and defeating the purpose
of content negotiation.



Patrick Stickler, Nokia/Finland, (+358 40) 801 9690, patrick.stickler@nokia.com
Received on Friday, 10 January 2003 05:05:33 UTC

This archive was generated by hypermail 2.3.1 : Wednesday, 7 January 2015 15:32:36 UTC