[idn] Allowed/disallowed characters (was: Proposed suggestions ...)

[Maurizio Codogno <mau@beatles.cselt.it>]

 Paul Hoffman:

> >If some characters are disallowed, then it does not matter how much (or
> >little) we have in the list. The algorithm is the same, only diff is how big
> >the list/table is.
> 
> As long as there is an obvious set of characters for the list, we 
> completely agree. "Non-alphanumeric ASCII" is easy to add to the list in a 
> definitive fashion. "Punctuation" is much harder (outside of the ASCII 
> range), especially because some new punctuation characters will be added in 
> the future. The same is true for "symbols". Even "digits" gets tricky, 
> because some cultures will want their own digits that look quite different 
> than US-ASCII digits.

I still doubt whether the "disallowed list" is the best way to cope with
disallowed list" is the best way to cope with
the problem, unless we state that any character which is not present 
today on Unicode.

ciao, .mau.