Re: Question about the On Linking Alternative Representations TAG Finding

Raman --

I've been writing a much longer response, which incorporates the
scenarios with multiple Accept: values ... and I will continue work
on that, as I think getting this all clear in one place will be of
value to more than myself, but ...


* T.V Raman [2008/08/06 09:22 AM -0700] wrote:
> The question you ask is an interesting one, and in terms of Web
> Architecture in this regard, I've usually managed to preserve my
> sanity in the last 15 years by following the maxim "dont look
> more than one level deep in a recursive pattern".
>
...
>
> 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?

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



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Received on Wednesday, 6 August 2008 17:20:58 UTC