Proposal to remove Preferred-Value field for region YU in LTRU

Doug Ewell doug at
Sat Feb 21 21:04:32 CET 2009

The LTRU Working Group needs the help of ietf-languages and the Reviewer 
to make a decision.

In LTRU, where we are finishing work on RFC 4646bis and 4645bis, there 
is a plan to change the Preferred-Value for subtags that point to other 
subtags that also have Preferred-Values.  The goal is to have 
Preferred-Value always point to the "real" preferred value instead of 
making the user (human or software) follow a chain.  In other words, 
instead of "A" -> "B" -> "C", we would have "A" -> "C", where the arrow 
represents a Preferred-Value link.

This is primarily necessitated by the addition of the ISO 639-3-based 
subtags, which are intended to supersede RFC 3066 registered tags and 
variant subtags whenever possible.  For example, we currently have 
"i-hak" -> "zh-hakka" for Hakka.  In RFC 4646bis, we will have the 
639-3-based subtag "hak", meaning that the Preferred-Value chain will 
become "i-hak" -> "zh-hakka" -> "hak".  We plan to change the 
Preferred-Value for "i-hak" to "hak" to eliminate this indirection.

Our question has to do with applying this logic to a particular region 
subtag.  Currently "YU" is deprecated with a Preferred-Value of "CS", 
and "CS" is deprecated with no Preferred-Value at all, since there is no 
single successor country.  It might make more sense to remove the P-V 
from "YU" altogether, to prevent the user from following a chain which 
ultimately leads to a dead end.  However, RFC 4646, Section 3.1 does not 
permit this group to remove a Preferred-Value, although the proposed 
4646bis will allow this.

As part of the production of a replacement Registry in draft-4645bis, it 
has been proposed to remove the Preferred-Value from "YU" -- as an LTRU 
change -- and optionally replace it with a Comments field such as 
"Comments: see BA, HR, ME, MK, RS, or SI".  This might be considered 
analogous to the existing Comments field for "CS".  It might also be 
preferred by those who feel that "CS" was not a suitable P-V for "YU" in 
the first place.

It has been objected that this type of change needs to be made by 
ietf-languages and the Reviewer, once 4646bis is approved and published 
and allows it, and should not be made by LTRU in the replacement 

Please send opinions, preferences, and comments to this list.

Doug Ewell  *  Thornton, Colorado, USA  *  RFC 4645  *  UTN #14  ˆ

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