I-D Action:draft-faltstrom-5892bis-02.txt

Mark Davis ☕ mark at macchiato.com
Mon Feb 21 22:29:43 CET 2011

That is a red herring. Computation of the characters needed to add to
Section G for stability *can* be done purely algorithmically.

   - For any new Unicode version V, look at DISALLOWED.
   - If it contains any characters that were PVALID, CONTEXTO, or CONTEXTJ
   when computed according to Unicode V-1, then add them to Section G, with
   their V-1 value.

Moreover, the Unicode consortium offered several times during the
development of IDNA2008 to institute a new derived Unicode property that
would make this even simpler, without needing access to the previous version
of Unicode. It would look something like Other_ID_Continue in


2011/2/21 Patrik Fältström <patrik at frobbit.se>

> On 21 feb 2011, at 21.58, Simon Josefsson wrote:
> > I didn't understand John's argument that we have an incompatibility
> > regardless of what we do
> Either we have stability in the algorithm (as now proposed) or we have
> stability in the table which is the result of the calculation of the
> algorithm.
> IDNA2008 is defined as being an _algorithm_ that should be stable, so an
> application can apply it regardless of what version of Unicode we talk
> about.
> Because the algorithm is based on property values that now changes for
> three codepoints, the result of the calculation is not stable.
> The alternative would be to change the algorithm, and that would make the
> codepoints not change, but the algorithm changes.
> IDNA2003 was a table based solution.
> IDNA2008 is an algorithm based solution.
>   Patrik
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