Subject: Re: [iucg] mappings-01 and the general procedure

From: John C Klensin <[email-masked]>
Date: Wed, 15 Jul 2009 09:12:27 -0400

--On Tuesday, July 14, 2009 12:00 +0200 Alessandro Vesely
<[email-masked]> wrote:

> Since this is a theoretical enumeration, there's another two
> classes of possibilities that may be worth mentioning, just
> for the sake of completeness:
> 
> * Match all of "a", "A", "á", "Á", "å", "Å", etcetera.
> Possibly also match "l" and "1", like old typewriters, so
> that, e.g., "paypal" and "paypa1" match. A procedure could
> even do complicate phonetics processing.

Yes.  Of course, matching all of those decorated characters to
each other and to the basic Latin forms would largely eliminate
at least some of the primary reasons for doing IDNs at all, at
least for extended Latin characters.  Patrik's example for
Swedish is only one example here: depending on language, some
"decorated" Latin characters are really separate characters that
cannot possibly match and others (or the same ones in a
different language) may be optional, or semi-optional accents,
phoneme-modifiers, or stress marks.   But it is logically
possible.

> * Define the mapping parametrically in _mapping.TLD, for each
> IDN-enabled TLD. Even if this may answer what are TLDs good
> for, a global mapping would still be needed for the tld label
> itself.

I haven't thought about this enough to say "impossible", but I
don't think it could be made to work in an acceptable way in
practice.   First, there is really no such thing as an
"IDN-enabled TLD" unless you mean "TLDs who were required to ask
ICANN for permission, or who asked as a courtesy, and got that
permission".  The number who are required to ask is a small
fraction of the total number of TLDs.  Second, that permission,
or lack thereof, applies only at the second level.  If I'm got
control of the zone for BigMultinational.SomeTLD, then I can put
IDNs in my zone regardless of what permissions the registry to
SomeTLD has or needs.  

And, finally and most important, and again using
BigMultinational.SomeTLD as an example, it would be perfectly
natural for me to set up national, regional, or language
subdomains to reflect my business organization or marketing
policies.  The domains en-uk.BigMultinational.SomeTLD,
en-us..BigMultinational.SomeTLD, de-de.BigMultinational.SomeTLD,
de-ch.BigMultinational.SomeTLD, fr.BigMultinational.SomeTLD,
cn.BigMultinational.SomeTLD, jp.BigMultinational.SomeTLD, and so
on are all rational, reflect contemporary practice in many
organizations, and would probably all consider different mapping
rules appropriate.  That means _mapping.TLD really needs to be
_mapping.ParentDomain.  And that then gets tied up with the
CNAME/ DNAME problem and figuring out which parent domain is
really intended, probably rules for searching up the tree for
grandparent domains if there is no table at a given level.  

It may not be impossible, but I don't think it is even vaguely
plausible given the DNS.

   john