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

Re: Draft finding - "Transitioning the Web to HTTPS"

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Tue, 17 Feb 2015 13:48:25 +0000
To: Julian Reschke <julian.reschke@gmx.de>
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>
Message-ID: <f5bfva4odhy.fsf@troutbeck.inf.ed.ac.uk>
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
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.

ht

[1] http://tools.ietf.org/html/rfc7231#section-3.4.2
-- 
       Henry S. Thompson, School of Informatics, University of Edinburgh
      10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
                Fax: (44) 131 650-4587, e-mail: ht@inf.ed.ac.uk
                       URL: http://www.ltg.ed.ac.uk/~ht/
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Received on Tuesday, 17 February 2015 13:48:57 UTC

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