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Re: Request that the WG reconsider section 3.4: Content Negotiation

From: Mark Nottingham <mnot@mnot.net>
Date: Mon, 4 Nov 2013 15:12:34 -0800
Cc: "Henry S. Thompson" <ht@inf.ed.ac.uk>, HTTP Working Group <ietf-http-wg@w3.org>, "apps-discuss@ietf.org Discuss" <apps-discuss@ietf.org>, "www-tag@w3.org WG" <www-tag@w3.org>
Message-Id: <A5688D93-1195-4955-B990-0A499885027F@mnot.net>
To: "Julian F. Reschke" <julian.reschke@gmx.de>
What Julian says. Reactive negotiation is very common; formats are coming up with mechanisms for it all the time (e.g., the work on srcset, etc. in the W3C web perf WG).

Cheers,


On 4 Nov 2013, at 2:55 pm, Julian Reschke <julian.reschke@gmx.de> wrote:

> On 2013-11-04 17:53, Henry S. Thompson wrote:
>> It's my impression that content negotiation hasn't turned out to play
>> the kind of significant role in Web Architecture in general, or in
>> HTTP use in particular, that was expected for it.
>> 
>> I think the section on conneg in p2-semantics [1] is so out-of-step
>> with actually deployment, usage and expectations that to publish it as
>> it stands would be a serious mistake.
>> 
>> In particular, the discussion of the relative disadvantages of the
>> newly (re-)named 'proactive' and 'reactive' variants are not only
>> out-of-date, but also this discussion appears to at least this reader
>> to amount to a recommendation for 'reactive' negotiation.  Yet as far
>> as I can tell no user agents _or_ servers actually support this
>> approach today, as it's described here.
>> 
>> I was sufficiently concerned about this question to undertake a
>> moderately extensive empirical investigation [2].  To summarise
>> perhaps too briefly, I found _no_ evidence of the use of reactive
>> conneg in over 75 million HTTP request/response exchanges.
>> ...
> 
> 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. That's what the
> 
> "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."
> 
> in <http://greenbytes.de/tech/webdav/draft-ietf-httpbis-p2-semantics-24.html#rfc.section.3.4.2.p.1> is about.
> 
> Best regards, Julian

--
Mark Nottingham   http://www.mnot.net/
Received on Monday, 4 November 2013 23:13:01 UTC

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