Punycode & IMA/EAI

Shawn Steele Shawn.Steele at microsoft.com
Thu May 22 19:04:14 CEST 2008

The apparently subtle point I'm trying to make, which does apply to the draft, apparently has been lost in the drifting of the thread.

- Shawn.

-----Original Message-----
From: John C Klensin [mailto:klensin at jck.com]
Sent: Wednesday, May 21, 2008 10:56 PM
To: Shawn Steele; Tina Dam; Martin Duerst; Felix Sasaki
Cc: idna-update at alvestrand.no
Subject: RE: Punycode & IMA/EAI

--On Wednesday, 21 May, 2008 13:06 -0700 Shawn Steele
<Shawn.Steele at microsoft.com> wrote:

> b) if there is such a requirement to lookup unknown punycode,
> then there must be a provision to also allow converting
> Unicode code points to punycode.  This isn't a problem if the
> Unicode is "normalized".  It could be a problem if the Unicode
> is in a case mapped form or other form that might not make the
> conversion straightforward.


I'm still not sure I understand what you are getting at here,
unless it is a return to the discussion of just storing UTF-8 in
the DNS rather than using punycode encoding or some other ACE.
But, to the issue above, this is one of the key reasons why the
design of IDNA2008 advocates moving to as little mapping as
possible.   We are going to need to be sensitive to transition
arrangements, but, for the reasons you cite (again, if I
understand them) having a fully reversible U-label <-> A-label
mapping is actually fairly important to users... and,
conversely, one of the issues with IDNA2003 is precisely "user
puts a string in, it gets converted to punycode form, it gets
converted back, user doesn't recognize result".

There are obvious and difficult tradeoffs here and IDNA2003
wasn't "wrong".  It just appears that making the tradeoff the
other way and moving in that direction as quickly as possible
is, on balance and with experience, a better choice.


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