Stability of valid IDN labels

[Andrew Sullivan]

On Sat, Apr 19, 2008 at 06:51:55PM -0400, John C Klensin wrote:

> In a sense, the real stability criterion one would like is "if this was 
> valid at the time it was registered, then it is valid forever".  
> Unfortunately, that criterion is impossible to state, much less enforce, 
> given the many millions of zones in the DNS.

So for practical purposes, isn't it enough to say, "Once a character
is valid, it is valid forever," irrespective of whether it is in fact
ever registered?  This solves the problem that you can't practically
know all the names actually registered in the DNS.  (I realise it
entails the cost that, if we're wrong in some serious way about a
character, we have to live with it forever.  That just seems to me
like a good incentive to be as conservative as possible when adding
things to the exceptions list.)

A

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Andrew Sullivan
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