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Re: Question about the On Linking Alternative Representations TAG Finding

From: Richard Cyganiak <richard@cyganiak.de>
Date: Wed, 6 Aug 2008 19:51:21 +0100
Cc: "T.V Raman" <raman@google.com>, seb@serialseb.com, www-tag@w3.org, kidehen@openlinksw.com
Message-Id: <74557A97-0D79-44CA-85F7-E6CAAE7DCA7B@cyganiak.de>
To: Ted Thibodeau Jr <tthibodeau@openlinksw.com>

Ted,

On 6 Aug 2008, at 18:19, Ted Thibodeau Jr wrote:
>> Returning to your final question, where the user-agent does
>> content-negotiation, indicates a preference for one type, but
>> asks by URI for the other, I would say respect the URI. I dont
>> claim this to be *correct* in any sense, other than that I would
>> break the tie this way. Reasoning: The client, by asking for a
>> URI that directly resolves to a given representation has
>> essentially bypassed content-negotiation.
>
> These two paragraphs seem to be at odds with each other.  (And
> I'm baffled as to why you would choose to respect the URI when
> you don't claim this behavior is *correct*.  Why not choose the
> correct behavior, when such can be determined, and has been,
> i.e., HTTP 406?)
>
> How is a Client Agent to know that the URI it has requested
> corresponds directly to a resource which content doesn't match
> its Accept: header?

I think you misunderstood Raman's message.

Raman was answering to a question of me: What should a server do if  
the client accepts formats A and B; accesses the resource specific to  
A; but expresses a preference of B over A. Should the server answer A  
or B? 406 is clearly not a sensible choice.

The waiter/restaurant/glass/ice analogy is misleading. Content  
negotiation isn't like a restaurant.

Best,
Richard



>
>
> It can only learn this if the Server delivers a 406 when such
> a mis-matched request is made.
>
> A 406 is the *only* response I can imagine which conforms both to
> the HTTP/1.1 specification *and* to Web architecture (which I do
> not see as in conflict, but that may be due to my perspective).
>
> To slightly modify an example Kingsley used on the LOD list, if
> I ask for water (i.e., "Accept: state/liquid") and you deliver
> ice ("state/solid") or steam ("state/vapor") -- has my request
> been satisfied?
>
> I think not -- and this is not too terribly far removed from the
> scenario where I request URI-a (Accept: text/plain) and you give
> me URI-a (application/binary).
>
> Tell me you don't have water, but you do have ice and steam --
> and let *me* decide what to do next.
>
> *This* is *negotiation*.
>
> Be seeing you,
>
> Ted
>
>
>
> -- 
> A: Yes.                      http://www.guckes.net/faq/ 
> attribution.html
> | Q: Are you sure?
> | | A: Because it reverses the logical flow of conversation.
> | | | Q: Why is top posting frowned upon?
>
> Ted Thibodeau, Jr.           //               voice +1-781-273-0900  
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Received on Wednesday, 6 August 2008 18:55:37 GMT

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