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Re: Hausenblas' request on format negotiation

From: Dan Connolly <connolly@w3.org>
Date: Wed, 25 Nov 2009 11:39:03 -0600
To: Larry Masinter <masinter@adobe.com>
Cc: Jonathan Rees <jar@creativecommons.org>, www-tag <www-tag@w3.org>, Julian Reschke <julian.reschke@greenbytes.de>
Message-ID: <1259170743.4804.1643.camel@pav.lan>
On Wed, 2009-11-25 at 07:17 -0800, Larry Masinter wrote:
> > I would also like to have on the agenda to dispose of Michael
> > Hausenblas's request for clarification on the of use content
> > negotiation [2], in one of the following ways:
> >  - reject
> >  - refer Michael to HTTP WG
> >  - accept as new issue
> >  - accept under ISSUE-57
> Hausenblas' question:
> > Please note that I don't ask if this works. It does. Obviously. The
> > question, to put it in other words, is: is the PNG *representation* derived
> > via conneg from the generic resource <http://sw-app.org/sandbox/house>
> > equivalent to the RDF in Turtle?
> > If not, why not? If it is, can you please point me to a finding, note, a
> > specification, etc. that 'normatively' defines what 'equivalency' really is?
> IMHO, the architecture of content negotiation is (in HTTP or elsewhere) is
> based on the notion that is that it is the responsibility of the 
> information supplier (HTTP server in this case) to determine what
> is equivalent for the purpose of this communication.

I Agree.

This is what webarch says, too, I think... hmm... it
seems to only say something about the case of fragment ids:

"The second case is a server management error: representation providers
must not use content negotiation to serve representation formats that
have inconsistent fragment identifier semantics."
  -- http://www.w3.org/TR/webarch/#frag-coneg

> That is, there is no external authority to disallow sending a PNG and
> a text/turtle version as "equivalent". Whether the server is behaving
> reasonably, though, and not sending the client gibberish, is the
> server's responsibility. 
> Issue 57 would be inappropriate.  I suppose we should consider, though,
> whether the response of ACTION-231 for ISSUE-53 might be insufficient?


> I.e., 
> http://lists.w3.org/Archives/Public/ietf-http-wg/2009JulSep/0763.html
> should add a sentence, e.g.,
> < Note that the supplier of representations (or choices) has the
> < responsibility of determining, for its purposes, which representations
> < might be considered to be the "same".

Yes, please.

I just noticed that Henry asked for something like that
(or rather: noted the lack of it) in a 2009-10-22 comment on

Dan Connolly, W3C http://www.w3.org/People/Connolly/
gpg D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Wednesday, 25 November 2009 17:39:08 UTC

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