Re: [Sip] language info in SIP headers

[Jonathan Rosenberg <jdrosen@dynamicsoft.com>]

Shingo Fujimoto wrote:
> I am happy to hear you already had some discussions.

Henning and I were trying to determine the "right" thing to
to regarding language tagging, and found, as you are
finding, that it is a far from simple answer....

specific comment inline:


> 
> Henning Schulzrinne wrote:
> 
> 
>>- RFC 2482 or http://www.unicode.org/unicode/reports/tr27/#tag provide
>>language tagging, as you noted. While I have not seen an official
>>statement from the IESG on this, I believe 10646 language tagging has
>>generally been deprecated. It's not quite clear whether the reasons (I
>>believe, nesting) for that apply to short text such as Subject or
>>Organization.
> 
> 
> 
> You are probably right.
> 
> Here is the comment from Ned Freed, one of the RFC2231 authors:
> 
> 
>>Language indicators in a pure UTF-8 environment like SIP headers have
> 
> to be
> 
>>stored as part of the UTF-8 string itself. The plane 14 language tags
> 
> described
> 
>>in
>>
>>   http://www.unicode.org/unicode/reports/tr27/#tag
>>
>>are the only means of doing this that I'm aware of. However, the use
>>of such tags is, as the text indicates, strongly discouraged.
>>
>>It is the Unicode Technical Committee's belief that
>>
>>  The requirement for language information embedded in plain text data
> 
> is often
> 
>>  overstated.
>>
>>As such, I see little chance for support for such tagging in the
> 
> context of SIP
> 
>>headers being widely deployed.
>>
>>				Ned


I think the point Ned is making here, is that language
tagging is not all that useful in practice. With UTF-8,
you can render Kanji characters. You need the language
tagging IFF some automata needs to do something special
based on knowledge of the language, such as translation
or text to speech. However, it is far from clear whether
that information is truly needed. Translation of names
(like those in Subject, From, To) is not likely to work
in any case, nor is it clear that the language tag is
needed for it...



> The reason I prefer this approach is that SIP messages must be small
> if it runs over UDP. "language tag" will add only few bytes.
> 

Well, as Ned indicated, and Henning repeated, the in-band
language tagging provided by UTF-8 is not considered
acceptable, and we would not be able to write a specification
which recommends it as the solution for sip.

-Jonathan R.
-- 
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
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