[idn] Re: Is space allowed in a hostname?

[Simon Josefsson <jas@extundo.com>]

John C Klensin <klensin@jck.com> writes:

[snip]
> NFKC is, IMO, guilty of one severe sin, and it is the one I
> believe Simon was pointing out (but it isn't a new observation
> either): it is not consistent when examined on a language by
> language and code-point by code-point basis.  If a single
> meta-rule could be made up that would identify the "right"
> choice for IETF and DNS purposes, it would handle some sets of
> characters consistently with the rule and some inconsistently.
> But, again, no better solution is on the table, and, in all
> likelihood, no objectively better solution is possible: no
> single, simple, statement can be made that accurately predicts
> whether characters are duplicated or unified in the
> Unicode/10646 code set itself.  The allocation decisions may
> well have been made rationally, but enough different rules were
> applied, and generic enough rules were applied, that it would be
> unreasonable to expect complete consistency with  any simple
> rule, much less an IETF-optimized one.
>
> It is all going to come down to arbitrary choices at some stage.
> Some of those arbitrary choices are going to irritate some
> groups of people and seem harmless to others.  If they were made
> a different way, different people would be irritated.
[snip]

This was a good summary.

I think the reason that I and others are bringing up old questions is
that several of us did participate when this working group started,
raising these questions.  We are now expecting that the documents
answer the questions, or where they cannot be answered to everyone's
agreement, at least say what inherent problems and risks are caused by
not solving the problems completely.  Since internationalized strings
is a tricky subject, it is IMHO as important to carefully describe
what problems are _not_ solved as to describe what problems actually
are solved.  Admittedly, the latest document revision fixed several of
my pet problems (thanks!), but being new to the topic and not having
read the specifications all that carefully makes me worry about there
being other inherent problems that aren't documented or discussed.