[idn] comments on IDNA-04

["James Seng/Personal" <jseng@pobox.org.sg>]

Sorry for duplicate: Previous one got send out accidently while still
editing.

-James Seng

---
The ToASCII operation takes a sequence of Unicode code points and
transforms it into a sequence of code points in the ASCII range (0..7F).
The original sequence and the resulting sequence are equivalent host
labels.

The ToUnicode operation takes a sequence of Unicode code points and
returns a sequence of Unicode code points. If the input sequence is a
host label in ACE form, then the result is an equivalent host label
that is not in ACE form, otherwise the original sequence is returned
unaltered.

JS>> Suggest to define ASCII Compatible Encoding (ACE) before using it.
then s/ToASCII/ToACE/.

ToACE operation takes a sequence of Unicode code points and transform it
into an ACE.

ToUnicode operation takes an ACE and return a sequence of Unicode code
points.

---
ToASCII consists of the following steps:

    1. If all code points in the sequence are in the ASCII range (0..7F)
       then skip to step 3.


JS>> Step 1 seem to be optimization, but not a required step.

---
The ACE prefix, used in the conversion operations (section 4), will
be specified in a future revision of this document. It will be two
alphanumeric ASCII characters followed by two hyphen-minuses. It MUST
be recognized in a case-insensitive manner.

JS>> Suggest s/ACE prefix/ACE tag/. An "ACE tag" could be a uniquely
defined prefix and/or suffix defined by IANA and not neccessary in the
form of xx--.

---
Internationalized host name data in zone files (as specified by section
5 of RFC 1035) MUST be processed with ToASCII before it is entered in
the zone files.

JS>> Dont think we should make a mistake to define zone file format. No
reasons Zone file cant be in UTF-8 so long ToASCII/ToACE is applied
before using it.

---
It is imperative that there be only one ASCII encoding for a particular
host name. ACE is an encoding for host name labels that use non-ASCII
characters. Thus, a primary master name server MUST NOT contain an
ACE-encoded label that decodes to an ASCII label. The ToASCII operation
assures that no such names are ever output from the operation.

JS>> An ACE label that decodes to ASCII label should be defination an
invalid ACE. You dont want this to happen in any place where ACE is
used, not just primary master name server.