support of metadata

[John C Klensin]

--On Monday, September 14, 2009 02:11 +0200 jean-michel bernier
de portzamparc <jmabdp at gmail.com> wrote:

> Dear colleagues,
> among the points we introduced during the WG/LC that have not
> been addressed yeat is the end to end support of script
> oriented metadata (one example being the French majuscules).
> Metadata can be supported either:
> 
> - explicitely through a specific new code from "unassigned" -
> since Language Tag and Private Use control are disallowed

As is any use of an UNASSIGNED code.  The use of such codes is a
protocol violation; conforming implementations will not look up
labels containing them.

> - implicitely through an unlike sequence of PVALID codes (ex:
> FE73-0061 ... 007A)

Since there is no prohibition on such strings, nothing prevents
you from using them and interpreting them in a special way,
assuming that FE73 is not problematic from a Bidi standpoint
(while it is identified as a "Arabic" character, the code point
does not appear in Arabic-Shaping.txt, which drives Bidi).
However, most applications globally will interpret them as valid
labels, many or most applications will warn against them as
mixing scripts, and attempts to use specific characters as
metadata indicators will not work satisfactorily except in your
particular applications.
 
> If I call "punnyplus" the extended algorithm that will provide
> this support: - in the first case there is no risk of
> confusion since it will only work if both ends are punnyplus
> enabled.

In the first case, anyone supporting "punnyplus" will be in
violation of IDNA.

> - in the second case there is no risk of confusion either but
> the sending end is to be punyplus enabled.

And the receiving system has to know to apply "punyplus" rules
rather than IDNA rules.

> If the WG documents remain unchanged in terms of French
> majuscules support, the support of the two will be offered as
> a response to the "+" entry. Ex. http://+Etat.fr.

That would be an interoperability problem.  I would be quite
surprised if FRNIC went along and more surprised if ICANN
permitted any gTLD to do this.

   john