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Re: [apps-discuss] Request that the WG reconsider section 3.4: Content Negotiation

From: Mark Nottingham <mnot@mnot.net>
Date: Tue, 5 Nov 2013 15:45:08 -0800
Cc: "Julian F. Reschke" <julian.reschke@gmx.de>, "www-tag@w3.org WG" <www-tag@w3.org>, HTTP Working Group <ietf-http-wg@w3.org>, "apps-discuss@ietf.org Discuss" <apps-discuss@ietf.org>
Message-Id: <93E08AC0-9D97-4296-B139-DE439D3DE8B2@mnot.net>
To: "Henry S. Thompson" <ht@inf.ed.ac.uk>
Hi Henry,

On 5 Nov 2013, at 4:18 am, Henry S. Thompson <ht@inf.ed.ac.uk> wrote:

>> 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
> How is this in scope for discussion _in the HTTP spec._?  People (not
> user agents, note) use 200 responses for a huge range of interesting,
> powerful, innovative things.  We don't look in the HTTP spec. to find
> a discussion of them.

You seem to be thinking of HTTP as a separate layer from the application; as section 3.4 of p2 says, itís defining a pattern of use, and that is certainly in scope for this specification, given that it was also in scope for RF2616.

> "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."
> "based on metadata included in the list"!  That's a specific reference
> to a 300 response.  There is no "list" in a 200 response, not that a
> user agent can detect anyway.

If there is more than one link in the response in *some* format thatís tied together in some fashion (e.g., with a link relation, as per RF5988), there certainly is a list available.

We talked about this issue at the WG meeting yesterday. Based upon that discussion, we decided to close this issue. Looking at <https://svn.tools.ietf.org/svn/wg/httpbis/draft-ietf-httpbis/latest/p2-semantics.html#content.negotiation>, I canít see any immediate clarifications that would help; if you can suggest some, please do bring them to our attention.


Mark Nottingham   http://www.mnot.net/
Received on Tuesday, 5 November 2013 23:45:36 UTC

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