Re: [Slim] Collapse attribute syntax to one line in draft-ietf-slim-negotiating-human-language

[Gunnar Hellström <[e-mail]>]

Den 2017-06-01 kl. 11:54, skrev Natasha Rooney:
> This seems sufficient given our previous conversations. q-values can 
> be applied within further work (although I don’t see why ordering 
> doesn’t do the job, works in web). 
It is not feasible to change syntax by adding q-values in an extension. 
That will cause interop problems, or complicated needs to negotiate 
protocol version. So, we need to decide the syntax now and stick closely 
to it.

Ordering is not sufficient because we have a need to set preferences 
between different media.
Ordering only works within a media.

And, a minor drawback: ordering does not allow to specify a number of 
languages in the same media with the same preference. One always will 
look as if it is more preferred than another. - but I think we can live 
with that.

Maybe the main question is: Will our own one-line syntax really be less 
complex to parse than the Accept-Language syntax that we might be able 
to find ready library routines for?
Adam Roach had views on complexity to parse different solutions. Maybe 
you, Adam can have a view on this?

Regards

Gunnar

>
> Bernard - any further thoughts?
>
> Natasha Rooney | Internet Engineering Director | Internet and Web Team 
> | Technology | GSMA | [e-mail] <mailto:[e-mail]> | +44 
> (0) 7730 219 765 | @thisNatasha | Skype: [e-mail] 
> <mailto:[e-mail]>
>
>> On 30 May 2017, at 00:04, Randall Gellens <[e-mail] 
>> <mailto:[e-mail]>> wrote:
>>
>> I uploaded version -10, which includes the syntax change to single 
>> line, along with a few editorial clarifications.  (Version -09 
>> accidently omitted an editorial clarification.)
>>
>> You can see a diff of the changes from 08 to 10 here:
>> https://www.ietf.org/rfcdiff?url1=draft-ietf-slim-negotiating-human-language-08&url2=draft-ietf-slim-negotiating-human-language-10
>>
>> If there objections to the change from multi-line to single-line, 
>> this can be reverted.
>>
>> --Randy
>>
>>
>>
>> At 2:57 PM -0700 5/28/17, Randall Gellens wrote:
>>
>>> In response to Adam Roach's comments as well as other comments, I 
>>> intend to update the draft to collapse the attribute syntax to one 
>>> line; each attribute can occur at most once per media, with all 
>>> languages on the same line.  This will further reduce the size of 
>>> the SDP block.
>>>
>>> If you object to this, please reply.
>>>
>>> Here is the section of Adam's review:
>>>
>>> At 8:31 PM +0000 3/28/17, Sabrina Tanamal via RT wrote:
>>>>  I'll note that much of this can be fixed if the syntax is collapsed so
>>>>  that each media section can have at most one hlang-send and one
>>>>  hlang-receive, each of which contain a list of one or more languages
>>>>  that can be sent or received. This is also much more consistent 
>>>> with the
>>>>  way SDP attributes are used in general. The presence of a "*" token on
>>>>  that line would indicate the "call should happen even without matching
>>>>  languages" characteristic; since there is only one place to add this
>>>>  indicator, the ambiguity of some lines indicating it and others not
>>>>  disappears. The preceding example would collapse to:
>>>>
>>>>  m=audio 49250 RTP/AVP 20
>>>>  a=hlang-send:es eu en *
>>>>  a=hlang-recv:es eu en *
>>>>
>>>>  ...and the example text would be revised to remove the implication 
>>>> that
>>>>  *sending* "es" necessarily implies *receiving* "es".
>>>>
>>>>  I'll further note that the majority of SDP libraries I've worked with
>>>>  would make accessing the all-on-one-line format easier than
>>>>  one-line-per-language as well.
>>>
>>> Here is the proposed ABNF:
>>>
>>>    Attribute Syntax:
>>>
>>>       hlang-value =  Language-Tag *( SP Language-tag ) [ SP asterisk ]
>>>
>>>                            ; Language-Tag as defined in BCP 47
>>>
>>>       asterisk    =  "*"   ; an asterisk (ASCII %2A) character
>>>
>>>       sp          =  1*" " ; one or more ASCII space (%20) characters
>>>
>>> --
>>> Randall Gellens
>>> Opinions are personal;    facts are suspect;    I speak for myself only
>>> -------------- Randomly selected tag: ---------------
>>> If forced to travel on an airplane, try and get in the cabin with
>>> the Captain, so you can keep an eye on him and nudge him if he
>>> falls asleep or point out any mountains looming up ahead ...
>>>        --Mike Harding, The Armchair Anarchist's Almanac.
>>>
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>>
>>
>> -- 
>> Randall Gellens
>> Opinions are personal;    facts are suspect;    I speak for myself only
>> -------------- Randomly selected tag: ---------------
>> Knowledge always desires increase; it is like fire, which must
>> first be kindled by some external agent, but which will afterwards
>> propagate itself.                       --Dr. Samuel Johnson
>>
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Gunnar Hellström
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