mappings-01 and the general procedure

[John C Klensin]

On Sun, Jul 26, 2009 at 06:37, Yoshiro YONEYA <yone at jprs.co.jp>
wrote:

> I'm wondering if the general procedure is applied to FULL STOP
characters.
> For example, Unicode string (FW- stands for Full Width)

--On Sunday, July 26, 2009 07:52 -0700 Mark Davis ⌛
<mark at macchiato.com> wrote:

> I agree that that should be done, but John Klensin was against
> it. Something about not being able to recognize separate
> labels (although current technology does it just fine).

Mark, it really is not that "I'm against it".  I've just
summarized, several times, some rather aggressive feedback we've
gotten about the issue.  To repeat that summary (in even briefer
form than before), there is a fairly fundamental DNS requirement
that one be able to convert labels from and to the external
(label.label...) form to the internal (length-label,
length-label,...) one without knowing anything about the labels
themselves, even if those labels are "just octets" rather than
anything that is specifically ASCII, LDH, UTF-8, etc.  In other
words, that conversion has to be able to be performed, not only
by IDNA-aware applications, but applications that don't make any
check at all about the contents of the labels.

As several people have pointed out, if one could somehow find a
character that is not actually used in the particular script of
interest and immediately map it at keyboard-> OS time into  a
period, there would be no problem.  But that character isn't
going to be on the user's keyboard, so it probably isn't a
solution to any interesting problem.   The difficulty with these
other dot-look-alikes is that they are important for other uses
in the relevant languages/scripts so that the notion of always
mapping them into something else doesn't work either.

     john