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Re: Using content negotiation to serve content variants to people wit h special needs?

From: Charles McCathieNevile <charles@w3.org>
Date: Wed, 19 Jun 2002 18:05:53 -0400 (EDT)
To: David Woolley <david@djwhome.demon.co.uk>
cc: <w3c-wai-ig@w3.org>
Message-ID: <Pine.LNX.4.30.0206191752400.17276-100000@tux.w3.org>

In general I agree with David's assessment - currently most Web designers
seem to have very little understanding of HTTP, which is important to content
negotiation. And most people still rely on an external provider to host
content, although more and more systems have web servers built in and people
could host their own content. (This doesn't apply too large sites who
generally do control their own systems).

Actually W3C does negotiate content-types and languages when there are
variants available - for example it is possible to request some documents as
html, plain text, or rdf, or for some resources to request them as an image
or as rdf...

To enable this to work with deep linking is actually not terribly difficult.
There are versions of a resource available in a specific type, with a URI,
and there is a URI for a resource that can be content-negotiated. For
example, http://www.w3.org/Icons/w3c_home is a W3C logo, and  might be served
as a GIF, a PNG, or in other forms. On the other hand
http://www.w3.org/Icons/w3c_home.gif is a GIF version of the W3C logo. Either
of these can be bookmarked, but it makes more sense in most cases to bookmark
the resource in its general version, not a specific representation of it.

(Actually the fact that it ends in .gif just shows the way our server is
configured - the relevant URIs could easily be .../jgfkgfjg and
.../87otygoybig and the system would still work.)

cheers

Chaals

On Wed, 19 Jun 2002, David Woolley wrote:


  > I wonder if anyone has tried to use HTTP content negotiation mechanism for
  > serving different variants according to special needs, e.g. to send a sign

  I think the problem with content negotiation is that it requires server
  configuration.  Most informational page developers are one technology people,
  and if it can't be done with a meta element in HTML, it can't be done at all,
  as HTTP is a foreign technology.

  Slightly more legitimate reasons are that sources of cheap web space tend
  not to allow any server configuration, so people learning can't play with
  it and people an a budget can't afford it.

  The more technical problems with language negotiation are that it is
  difficult to do well and maintain cachability (not that that seems to
  matter to todays designers) and it can be difficult to have a satisfactory
  way of overriding the negotiated language (without reconfiguring the browser.

  If one negotiates every page, one needs to reconfigure the browser.  If
  one only negotiates the home page, deep links will not benefit.  If one
  has a negotiation page that redirects into a non-negotiated page, for
  ever page, it may be difficult to convince people linking to the site to
  pick up the link to the negotiation page rather than the negotiated
  page they are viewing.

  The only real life negotiated pages I have come across are Windows Update
  and Google (W3C negotiates graphics formats).


-- 
Charles McCathieNevile    http://www.w3.org/People/Charles  phone: +61 409 134 136
W3C Web Accessibility Initiative     http://www.w3.org/WAI  fax: +33 4 92 38 78 22
Location: 21 Mitchell street FOOTSCRAY Vic 3011, Australia
(or W3C INRIA, Route des Lucioles, BP 93, 06902 Sophia Antipolis Cedex, France)
Received on Wednesday, 19 June 2002 18:05:59 GMT

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