W3C home > Mailing lists > Public > www-tag@w3.org > February 2015


From: Julian Reschke <julian.reschke@gmx.de>
Date: Tue, 17 Feb 2015 15:56:39 +0100
Message-ID: <54E356A7.5080107@gmx.de>
To: "Henry S. Thompson" <ht@inf.ed.ac.uk>
CC: "Eric J. Bowman" <eric@bisonsystems.net>, Mark Nottingham <mnot@mnot.net>, Noah Mendelsohn <nrm@arcanedomain.com>, "www-tag@w3.org List" <www-tag@w3.org>
On 2015-02-17 14:48, Henry S. Thompson wrote:
> Julian Reschke writes:
>> AFAIU, this is just a misunderstanding. I recommend reading the whole
>> thread, in particular
>> <https://lists.w3.org/Archives/Public/ietf-http-wg/2013OctDec/0531.html>.
> I don't see that anything I said is compromised by what you wrote
> there, i.e.
>    Reactive conneg isn't just about 300s and 406s. Another example
>    would be a representation returned with a 200 response that contains
>    links to alternate versions of the content.
> As I made clear in what I wrote, all I have is lack of evidence _for_
> reactive conneg.  What you describe above is not actually part of the
> HTTP _protocol_ at all -- it amounts to an observation that 200
> content may be interpretable by human beings to offer multiple choices

It doesn't have to be a human being. Link relations have been mentioned 

> for follow-up.  I also think that the following is ingenuous at best:
>    If the user agent is not satisfied by the initial _response
>    representation_, it can perform a GET request on one or more of the
>    alternative resources, selected based on metadata included in the
>    list, to obtain a different form of representation for that
>    response. Selection of alternatives might be performed automatically
>    by the user agent or manually by the user selecting from a generated
>    (possibly hypertext) menu.
>    Note that the above refers to _representations of the response_, in
>    general, not representations of the resource.  The alternative
>    representations are only considered representations of the target
>    resource if the response in which those alternatives are provided
>    has the semantics of being a representation of the target resource
>    (e.g., a 200 (OK) response to a GET request) [1] [emphasis added]
> This distinction between representations of resources and
> representations of responses is, as far as a quick search of the 723*
> family reveals, both unprecedented and unexplained.  But that's
> another topic, I guess.
> Wrt your point, I read the second paragraph from 7231 above as saying
> it's _not_ conformant, supposing I ask for a document from your site,
> to respond with a list of links to alternative representations of that
> document in a 200 response, because a 200 response says "here is a
> representation of the document you requested".  So I don't see how you
> could view such a response as a conformant example of reactive
> conneg---it's either not conformant, or not conneg.

It might be a full representation of the identified resource, 
*including* links to alternate versions. Think Wikipedia links to 
alternate language versions.

Best regards, Julian
Received on Tuesday, 17 February 2015 14:57:26 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 22:57:10 UTC