Subject: Re: [urn] 2141bis questions - (3) Section 4.1 "normalization" comment

From: John C Klensin <[email-masked]>
Date: Mon, 02 Feb 2015 16:05:22 -0500

Mark (and others),  
Sorry for the delay in responding.  You at least know what has
been taking up my time.

--On Wednesday, January 21, 2015 16:12 +0100 Mark Davis ☕️
<[email-masked]> wrote:

> While the situation with casing is not trivial, it is not as
> complicated as sometimes portrayed.
> 
> Unicode does have a 'case normalization', called "case
> folding", which erases case differences, and is widely
> deployed. In a few instances, it does not always match local
> conventions for casing (I can go into details if desired).
> Like normalization, it has stability guarantees (
> http://unicode.org/policies/stability_policy.html#Case_Folding
> ).
>...
> ​I do not wish to weigh in on whether comparison or storage
> should be case-sensitive or insensitive​; just wanted to
> point out that there is not a technical barrier if
> case-insensitivity is desired.

Most of the case issues are dictated by 3986 unless we make
explicit decisions for URNs to depart from them, probably on a
per-scheme basis rather than a per-NID one.  But I have to
slightly disagree about the technical barrier.   URNs are
another instance of a family of identifiers that, in general,
have no language or location context.  When case folding
interacts with a need for specific locale knowledge (dotless-i
and maybe Eszett are examples), then, while the number of cases
may be small (and almost certainly  is), those are the sorts of
things that cause some of us to urge caution and careful
consideration of both advantages and risks.

best,
    john