Changing DISALLOWED (was Re: Reserved general punctuation)

Andrew Sullivan ajs at
Thu May 1 18:38:40 CEST 2008

On Wed, Apr 30, 2008 at 07:17:56PM -0700, Mark Davis wrote:

> 1. We say that once DISALLOWED, always DISALLOWED.
> This is not a firm promise, because an obsoleting RFC could change it, but
> would certainly set a very high bar.
> 2. We say that characters can only be removed from DISALLOWED by an
> obsoleting RFC.
> A slightly lower bar. While it could be changed, it would certainly be
> difficult.

I'm not sure that I see what the practical difference is between these
two is.  In any case, I think it preferable that the RFC has to be
obsoleted than any other approach.  This is because the only other
approach I can think of is to turn the whole thing into a registry,
and then have expert reviews for changing the registry.  Given that we
seem to be worrying about an extremely unlikely corner case, I have
doubts that we'd be able to find expert enough review to feel
confident in the change.  And if we want wider review than that, it's
going to require an obsoleting RFC.  (It'd be nice if there was
another IETF way to do this, but if there is I'm not aware of it.)


> 3. We say that characters can only be removed from DISALLOWED by the
> committee/mechanism that controls CONTEXT/exceptions, and only in extremis.

as I think John says (or at least implies) elsewhere, until we see a
proposal for what this mechanism is, it's very hard to evaluate how
desirable this answer is.  

I guess this means I prefer 2, which in my view is practically
equivalent to 1.


Andrew Sullivan
ajs at
+1 503 667 4564 x104

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