Changing the xn-- prefix

Simon Josefsson simon at
Thu Mar 20 14:17:07 CET 2008

Paul Hoffman <phoffman at> writes:

> Given that this is a charter issue, not a post-charter issue, it would
> be good to get some closure here. Is anyone supporting changing the
> xn-- prefix other than Simon?

I never said that I support changing the xn-- prefix.  I believe it
would be quite unfortunate if we change the prefix.

However, I believe that ruling out changing the prefix in the WG charter
is premature.  How high the costs of changing the prefix will be depends
on the costs of changing other things in IDNA in backwards incompatible
ways, such as the encoding of ß.

Since the WG is empowered to make backwards incompatible changes, I
believe the WG should be equally empowered to consider whether changing
the prefix yield lower overall deployment costs.

I believe that the WG charter should say that the WG is:

  1) able to consider any backwards incompatible change, including the ß
  character and changing the prefix.

  2) not able to consider backwards incompatible changes at all, i.e.,
  that every string valid under IDNA2003 should remain valid and encode
  to the same value.

Considering that we are still discussing which changes is a good idea or
not, I think option 1) gives the WG better instruments to produce a
technically optimal solution given all constraints.


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