[Ltru] Re: Preferred-Value cycles (was: Registry deltas)

["Doug Ewell" <[e-mail]>]

Frank Ellermann <nobody at xyzzy dot claranet dot de> wrote:

> Last but not least it would eliminate the "hakka" reference in a 
> Preferred-Value, where "hakka" is the only "non-subtag" in any 
> reference.

You are presuming a rule where none exists.  A grandfathered tag may 
have another grandfathered tag as its Preferred-Value.  There is no 
restriction against this , no reason it should not be possible, and the 
fact there is only one such situation -- because two people 
independently happened to register tags for Hakka under RFC 1766 -- does 
not change any of that.

>> there is no "collision" between 5- to 8-letter language subtags (if 
>> any existed) and 5- to 8-letter variant subtags, any more than there 
>> is a collision between "ar" for Arabic and "AR" for Argentina.
>
> Of course there is for naive implementations, the theory of the 4646 
> structure is that you can decompose a tag into subtags, and still tell 
> what's what based alone on its length.

The theory is "length plus position" where position is relative to other 
subtags.

> 3 digits => UN number
> 3 alpha  => language (for 4646)
> 4 alpha at begin => language (reserved)
> 4 alpha later => script
> 4 alnum starting with a digit => variant
> 2 alpha at begin => language
> 2 alpha later => region
> 5..8 alpha at begin => language
> 5..8 alnum later => variant

You have created a slightly simplified, almost 100% accurate version of 
the real rules, described in RFC 4646 Section 2.2 ff.  It is not 100% 
accurate, though.

> In my old 4646 validator I've implemented this by adding a dummy 
> hyphen for anything that's not "at begin", and after that it was as 
> you said obvious that "AR" (case insensitive) is not "-AR".
>
> For 4646bis that isn't good enough anymore, because language and 
> extlang share the same namespace, as soon as there is a language "ang" 
> there can't be an extlang "-ang".

You don't need to do this.  If you are truly "validating," as opposed to 
checking well-formedness, you have to be using the Registry -- so you 
can simply look there to see whether a language "ang" exists and whether 
an extlang "ang" exists.

In my validator I used the real rules, and everything works just as well 
for 4646bis as for 4646.

--
Doug Ewell  *  Fullerton, California, USA  *  RFC 4645  *  UTN #14
http://users.adelphia.net/~dewell/
http://www1.ietf.org/html.charters/ltru-charter.html
http://www.alvestrand.no/mailman/listinfo/ietf-languages


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