Tables: BackwardCompatible Maintanence

Mark Davis mark at macchiato.com
Wed Dec 10 18:23:16 CET 2008


The situation on eszett was not an oversight in IDNA2003. It was discussed
at great length. And it is not a clear-cut case. There are a handful of
problematic cases:  eszett, final sigma, and the Turkish i's. These were all
ugly problems before Unicode; there wasn't much of a way around them. Had
the Germans had an uppercase eszett, the Greeks a final capital sigma, and
the Turks chosen a different accent on the i rather than have their casing
be inconsistent with every other Latin alphabet, it would have been far, far
easier for software. But Unicode has to recognize existing usage.

I still don't think I'm communicating well.

For the X/Y characters, the choices are:

BackwardCompatible automatic - stability is the norm, IETF can write RFC if
it wants to change to follow Unicode.

BackwardCompatible not automatic - instability is the norm, IETF can write
RFC if it wants to maintain stability.

Either of these two models can work - the first would be safer from a
stability point of view.

The only point about frequency is that we expect the X/Y character situation
to not occur very often, and not for very frequently-used characters. If the
frequency were higher, it would even more useful to promote stability, not
less. And having the BackwardCompatible table be automatically generated
promotes such stability.

Mark


On Wed, Dec 10, 2008 at 06:29, Erik van der Poel <erikv at google.com> wrote:

> On Tue, Dec 9, 2008 at 11:15 PM, Mark Davis <mark at macchiato.com> wrote:
> > Now, I do think that the likelyhood of the X/Y case happening is quite
> > small, and essentially zero with any frequently used characters.
>
> Eszett is frequently used. Yet, someone made a mistake there. Can you
> guarantee that we didn't make any mistakes with somewhat less
> frequently used characters?
>
> Or is the IETF community now saying that we will not make any future
> changes to PVALID and DISALLOWED, no matter how loudly the affected
> communities scream?
>
> Erik
>
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