Re: [core] [Last-Call] Call for comments on draft-ietf-core-problem-details-07

[Carsten Bormann <[e-mail]>]

On 2022-06-30, at 21:01, Randy Presuhn <[e-mail]> wrote:
> 
> However, I'd draw your attention to
> https://datatracker.ietf.org/doc/html/rfc5646#section-2.1.1

(Which indeed is referenced from that very note.)

> Requiring comparisons to be case-insensitive is not the same thing
> as requiring the canonical form to be lower case, particularly if
> these tags might be presented to humans somewhere along the way.

Right.

My personal knee-jerk reaction to case-insensitive data formats is to heavy-handedly force lower case in all places where this at all can be done.

So I would have used [a-z]{1,8}(-[a-z0-9]{1,8})* instead of [a-zA-Z]{1,8}(-[a-zA-Z0-9]{1,8})* as the regexp for a language tag.

But RFC 5646 Section 2.1.1 recommends a different preferred case, and unless someone can conjure a groundswell that this should be abandoned summarily right now, I would think it is the right thing to follow that recommendation, even if it has not been renewed for 13 years now (weaker versions of it also were in 4646 and 3066).  
On the other hand, trying to enforce the recommendation by mapping this recommendation to the regexp would make that very complicated again.
So we do have a somewhat complicated preferred encoding of the language tag, but it is not enforced.

I think we are in the right spot here.

Grüße, Carsten