Re: #428 Accept-Language ordering for identical qvalues
"Adrien W. de Croy" <adrien@qbik.com> Tue, 22 January 2013 09:33 UTC
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From: "Adrien W. de Croy" <adrien@qbik.com>
To: James M Snell <jasnell@gmail.com>, Mark Nottingham <mnot@mnot.net>
Cc: "Roy T. Fielding" <fielding@gbiv.com>, "Julian F. Reschke" <julian.reschke@gmx.de>, HTTP Working Group <ietf-http-wg@w3.org>
Date: Tue, 22 Jan 2013 09:30:54 +0000
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Subject: Re: #428 Accept-Language ordering for identical qvalues
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Just wondering if there is anything to be discussed about Accept-Encoding. There are some cases where it can cause issues for a cache. for example GET /something HTTP/1.1 Host: somewhere.com Accept-Encoding: gzip, deflate 200 OK HTTP/1.1 Content-Encoding: gzip Cache-Control: max-age=2000000 Vary: Accept-Encoding GET /something HTTP/1.1 Host: somewhere.com Accept-Encoding: deflate, gzip cache MUST NOT select 1st response due to difference in Accept-Encoding header between requests. Even though there's arguably no semantic difference. I've never seen a q value on Accept-Encoding, and the spec talks about transforming headers as part of matching, but it only allows adding / removal of LWS and combining multiples. Not re-ordering. I know there's the pathological case about something returning the headers of the request, but it seems like a big price to pay for this. Maybe all browser vendors should always order Accept-Encoding tokens in the same order. Adrien ------ Original Message ------ From: "James M Snell" <jasnell@gmail.com> To: "Mark Nottingham" <mnot@mnot.net> Cc: "Roy T. Fielding" <fielding@gbiv.com>; "Julian F. Reschke" <julian.reschke@gmx.de>; "HTTP Working Group" <ietf-http-wg@w3.org> Sent: 22/01/2013 6:58:35 p.m. Subject: Re: #428 Accept-Language ordering for identical qvalues >+1 on this... in the end, it's far better to have all the similar >things acting in the same way. Not only does that help developers, it's >going to help us make improvements in 2.0 and beyond. > > >On Mon, Jan 21, 2013 at 2:41 AM, Mark Nottingham <mnot@mnot.net> wrote: >> >>On 21/01/2013, at 7:37 PM, Roy T. Fielding <fielding@gbiv.com> wrote: >> >> > On Jan 20, 2013, at 1:51 PM, Mark Nottingham wrote: >> >> On 20/01/2013, at 11:52 PM, Roy T. Fielding <fielding@gbiv.com> >>wrote: >> >> >> >>> On Jan 19, 2013, at 6:34 PM, Mark Nottingham wrote: >> >>> >> >>>> Julian et al, >> >>>> >> >>>> I think the important bit here is the context that we're talking >>about the semantics of an expressed preference -- which can be freely >>ignored, or selectively applied, without affecting conformance. The >>important thing is that the preference itself have clear semantics, >>which I think Roy's change does (especially in concert with changes >>elsewhere). >> >>>> >> >>>> As such, I think the relevant question is whether this is >>specific to A-L, or all A-* that take qvalues. Roy, thoughts? >> >>> >> >>> I am pretty sure it is specific to languages. Accept has never >>been >> >>> treated as an ordered list, Accept-Encoding was originally >>designed >> >>> to prefer the smallest representation (changing that to qvalues >>was >> >>> unfortunate), and Accept-Charset is almost deprecated at this >>point. >> >> >> >> >> >> So, wouldn't the same arguments (minus the implementation status) >>apply to Accept? >> >> >> >> I.e., if it's just a preference, and the server is free to choose >>among the preferences anyway (or even ignore them), why *not* say >>Accept is ordered? >> > >> > I don't see any value in that given the lack of users setting the >> > values for Accept directly (outside of command-line tool usage) >> > and no assumption among UAs that Accept is ordered. >> > >> > Apache httpd resolves ties in type negotiation using the >> > internal ordering of representation variants. That is unlike >> > languages, for which the code deliberately checks the order received >> > in Accept-Language for resolving ties. >> > >> > Regarding proactive negotiation in HTTP/2, I'll note that Waka >> > strips all negotiation fields. I find the entire feature revolting, >> > from every architectural perspective, and would take the opportunity >> > of 2.x to remove it entirely. >> >> >>The value is that Accept-* headers all use qvalues the same way, which >>is much less confusing for pretty much everybody, and paves the way >>for a potentially simpler approach in 2.0 (your feelings about having >>proactive negotiation at all noted). >> >>Again, implementations are free to ignore it -- this is merely the >>semantics of the preference, not constraints on how it's followed. >> >> >>-- >>Mark Nottingham http://www.mnot.net/ >> >> >> >> >
- #428 Accept-Language ordering for identical qvalu… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Martin J. Dürst
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Roy T. Fielding
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Roy T. Fielding
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Amos Jeffries
- Re: #428 Accept-Language ordering for identical q… Martin J. Dürst
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Amos Jeffries
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Amos Jeffries
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Roy T. Fielding
- Re: #428 Accept-Language ordering for identical q… Nicholas Shanks
- Re: #428 Accept-Language ordering for identical q… Amos Jeffries
- Re: #428 Accept-Language ordering for identical q… Nico Williams
- Re: #428 Accept-Language ordering for identical q… Adrien W. de Croy
- Re: #428 Accept-Language ordering for identical q… Adrien W. de Croy
- Re: #428 Accept-Language ordering for identical q… Amos Jeffries
- Re: #428 Accept-Language ordering for identical q… Mark Nottingham
- Re: #428 Accept-Language ordering for identical q… Roy T. Fielding
- Re: #428 Accept-Language ordering for identical q… Mark Nottingham
- Re: #428 Accept-Language ordering for identical q… James M Snell
- Re: #428 Accept-Language ordering for identical q… Mark Nottingham
- Re: #428 Accept-Language ordering for identical q… Adrien W. de Croy
- Re: #428 Accept-Language ordering for identical q… Amos Jeffries
- Re: #428 Accept-Language ordering for identical q… Mark Nottingham
- Re: #428 Accept-Language ordering for identical q… Roy T. Fielding
- Re: #428 Accept-Language ordering for identical q… Mark Nottingham
- Re: #428 Accept-Language ordering for identical q… Nicholas Shanks
- Re: #428 Accept-Language ordering for identical q… James M Snell
- Re: #428 Accept-Language ordering for identical q… Adrien W. de Croy
- Re: #428 Accept-Language ordering for identical q… Amos Jeffries
- Re: #428 Accept-Language ordering for identical q… Adrien W. de Croy
- Re: #428 Accept-Language ordering for identical q… Roy T. Fielding
- Re: #428 Accept-Language ordering for identical q… Adrien W. de Croy
- Re: #428 Accept-Language ordering for identical q… Nicholas Shanks
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Mark Nottingham
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Roy T. Fielding
- Re: #428 Accept-Language ordering for identical q… Mark Nottingham
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Amos Jeffries
- Re: #428 Accept-Language ordering for identical q… Amos Jeffries
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Amos Jeffries
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Mark Nottingham
- Re: #428 Accept-Language ordering for identical q… Martin J. Dürst
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Julian Reschke
- Re: #428 Accept-Language ordering for identical q… Martin J. Dürst
- Re: #428 Accept-Language ordering for identical q… Mark Nottingham
- Re: #428 Accept-Language ordering for identical q… Eric J. Bowman
- Re: #428 Accept-Language ordering for identical q… James M Snell
- Re: #428 Accept-Language ordering for identical q… Martin Thomson
- Re: #428 Accept-Language ordering for identical q… Eric J. Bowman
- Re: #428 Accept-Language ordering for identical q… Roy T. Fielding
- Re: #428 Accept-Language ordering for identical q… Eric J. Bowman
- Re: #428 Accept-Language ordering for identical q… Nicholas Shanks
- Re: #428 Accept-Language ordering for identical q… Julian Reschke