Re: #428 Accept-Language ordering for identical qvalues

Julian Reschke <julian.reschke@gmx.de> Fri, 25 January 2013 13:58 UTC

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Date: Fri, 25 Jan 2013 14:55:48 +0100
From: Julian Reschke <julian.reschke@gmx.de>
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Subject: Re: #428 Accept-Language ordering for identical qvalues
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On 2013-01-25 14:02, Julian Reschke wrote:
> On 2013-01-25 07:16, Julian Reschke wrote:
>> On 2013-01-25 06:31, "Martin J. Dürst" wrote:
>>> On 2013/01/25 8:37, Mark Nottingham wrote:
>>>> Removing the text does seem like the most expedient path forward.
>>>>
>>>> That said, I don't find it particularly satisfying; our job is to
>>>> improve interop, and when there are latent semantics that aren't
>>>> documented, we have to consider whether we're doing it well.
>>>>
>>>> I propose:
>>>>
>>>> """
>>>> Note that some recipients treat language tags that have the same
>>>> quality values (including when they are both missing) to be listed in
>>>> descending order of priority. However, this behaviour cannot be relied
>>>> upon, and if their relative priority is important, it ought to be
>>>> communicated by using different quality values.
>>>> """
>>>>
>>>> ... because I think it best captures where we're at.
>>>
>>> Maybe I'm getting this wrong, but it sounds to me that Julian is
>>> insisting that it's okay to send arbitrary replies (e.g. once French,
>>> once English at random) if there are no q-values. It has been very
>>
>> It is, according to the spec. If it hurts, don't do it (thus add
>> qvalues).
>>
>>> clearly explained that this is highly confusing (in other words, bad for
>>> interoperability). Even if the current spec allows this, it would be
>>> good to have some text in the new spec that says that's a bad idea.
>>
>> We could also say that leaving the choice to the server might lead to
>> different languages being picked in subsequent requests.
>>
>>> Otherwise, I'm fine with the above Note, except for a small nit:
>>> Please change "including when they are both missing" to "including when
>>> they are missing", because there may be more than two missing (or equal)
>>> q-values.
>>>
>>> Regards,   Martin.
>>
>> Best regards, Julian
>
> Proposed change:
> <http://trac.tools.ietf.org/wg/httpbis/trac/attachment/ticket/428/428.diff>.
>
>
> This removes the new text about ordering, and adds the note below:
>
>  >       Note: Some recipients treat language tags that have the same
>  >       quality values (including when they are missing) to be listed in
>  >       descending order of priority.  However, this behavior cannot be
>  >       relied upon, and if their relative priority is important -- such
>  >       as for consistent results for a sequence of requests -- it ought
>  >       to be communicated by using different quality values.
>
> Feedback appreciated, Julian

In the meantime, Roy resolved this in 
<http://trac.tools.ietf.org/wg/httpbis/trac/changeset/2163>, which works 
for me as well:

"Note that some recipients treat the order in which language tags are 
listed as an indication of descending priority, particularly for tags 
that are assigned equal quality values (no value is the same as q=1). 
However, this behavior cannot be relied upon. For consistency and to 
maximize interoperability, many user agents assign each language tag a 
unique quality value while also listing them in order of decreasing 
quality. Additional discussion of language priority lists can be found 
in Section 2.3 of [RFC4647]."

Best regards, Julian