wrt IDNA2008 migration (was: IDN processing-related security considerations for draft-ietf-websec-strict-transport-sec)

Mark Davis ☕ mark at macchiato.com
Tue Oct 4 05:59:55 CEST 2011

*— Il meglio è l’inimico del bene —*

On Sun, Oct 2, 2011 at 05:57, John C Klensin <klensin at jck.com> wrote:

> --On Saturday, October 01, 2011 17:27 -0700 Mark Davis ☕
> <mark at macchiato.com> wrote:
> > The third choice, of course, was to maintain backwards
> > compatibility with 2003 for all characters in Unicode 3.2, and
> > just extend the same principles to new characters. That is a
> > much easier migration path...
> Unfortunately, that level of compatibility would have
> permanently doomed those who believe that ZWJ and ZWNJ (and some
> other "map to nothing" cases) to permanently living with
> distinctions that they consider very important.  Perhaps that
> would have been the right answer but, again, it wasn't what the
> WG decided on.

Actually, it would not have been. Sean Steele of Microsoft came up with a
nice technical solution to that, allowing the display of IDNs with the
ZWJ/NJ. But see below as well.

And ZWJ/NJ is, also, only two of thousands of incompatibilities introduced
by 2008.

> > We've seen this before. XML 1.1 only had a small
> > breaking-compatibility changes, but those changes were enough
> > to completely doom it.
> Although the jury is still out, the same could be said for IPv6.
> To the extent that analogy is relevant, one might suggest that
> there weren't enough perceived benefits in XML 1.1 and IPv6 to
> justify dealing with the incompatibilities... or the conversion
> and deployment costs whether or not the incompatibilities
> existed.  It is harder to prove that the incompatibilities alone
> are to blame.
> On the other hand, if strict backward-compatibility with
> deployed technologies were always the right answer, we wouldn't
> need to be having discussions about conversions of
> tungsten-filament incandescent lighting to CFLs and LEDs because
> we would still be using candles and gas or, to use an older
> analogy, we would be worried about a rather different sort of
> pollution and waste problem in our cities than emissions from
> automobiles.

What you say is a false dichotomy, of course: saying that there were only
two alternatives: (a) complete stasis or (b) breaking backwards

There are other alternatives. The obvious one is, well,
*maintaining*backwards compatibility. In this case, it would provide

   - Every valid 2003 IDN remains valid under 2008
   - Additional valid IDNs are allowed under 2008: with either post Unicode
   3.2 characters or those unmapped by 2003.

>    john
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> Idna-update at alvestrand.no
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