Subject: Re: [Slim] Syntax of combination of language tag and Advisory vs Required indication in draft-ietf-slim-negotiating-human-language

From: "Doug Ewell" <[email-masked]>
Date: Thu, 28 Jul 2016 12:02:48 -0700

Gunnar Hellström wrote:

> This would be a valid subset ( if we do not do anything to issues 1
> and 2 above):
>
> humintlang-send  =  "a=humintlang-send" HCOLON
>                      [ language *(COMMA language) ]
> language         =  language-range
> language-range   =  ( ( 1*8ALPHA ) / "*" )

Specifying language-range as 1*8ALPHA conflicts with the SHOULD and
RECOMMENDED wording in Section 6.2: 

> Each value MUST be a language tag per RFC 5646 [RFC5646].  RFC 5646
> describes mechanisms for matching language tags.  While RFC 5646
> provides a mechanism accommodating increasingly fine-grained
> distinctions, in the interest of maximum interoperability for real-
> time interactive communications, each 'humintlang-send' and
> 'humintlang-recv' value SHOULD be restricted to the largest
> granularity of language tags; in other words, it is RECOMMENDED to
> specify only a Primary-subtag and NOT to include subtags (e.g., for
> region or dialect) unless the languages might be mutually
> incomprehensible without them.

There are legitimate use cases for specifying additional subtags. If a
caller requests a text stream in Chinese (or Serbian), she might need to
specify Traditional vs. Simplified Chinese (or Cyrillic vs. Latin
script), or risk losing comprehensibility.

Additionally, 1ALPHA and 4ALPHA are pointless as part of this rule,
since they cannot be valid BCP 47 tags.

A better and simpler syntax would be:

humintlang-send  =  "a=humintlang-send" HCOLON
                     [ language *(COMMA language) ]
language         =  Language-Tag

where Language-Tag is defined in RFC 5646, Section 2.1.

Any asterisks or plus signs or what have you, if agreed upon, could then
be added to the humintlang-send and/or humintlang-recv definitions.

As a side note, while it is true that "RFC 5646 provides a mechanism
accommodating increasingly fine-grained distinctions," it is a common
myth that it *encourages* such lengthy tags. There is a section in RFC
5646 dealing with the principle "tag content wisely," which has to do in
part with omitting unnecessary subtags.

--
Doug Ewell | Thornton, CO, US | ewellic.org

---

From: Gunnar Hellström <[email-masked]>
Date: Fri, 29 Jul 2016 09:04:22 +0200

> be added to the humintlang-send and/or humintlang-recv definitions.
GH: Thanks for the correction.
> part with omitting unnecessary subtags.
GH: We discussed that there is a way to indicate translated in a subtag 
and that it may be desirable to include such information sometimes. Do 
you regard that still allowable?
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-- 
-----------------------------------------
Gunnar Hellström
Omnitor
[email-masked]
+46 708 204 288