Re: idna-bis and 'ß'

John C Klensin klensin at
Mon Nov 26 14:03:38 CET 2007

--On Monday, 26 November, 2007 13:20 +0100 Harald Tveit
Alvestrand <harald at> wrote:

> --On 26. november 2007 12:53 +0100 Thomas Roessler
> <roessler at> wrote:
>> On 2007-11-23 19:16:43 +0100, Harald Tveit Alvestrand wrote:
>>> It's an user interface issue what to do when the user types
>>> a LATIN SMALL LETTER SHARP S; idnabis deliberately does not
>>> require that one maps it to "ss".
>> It is *not* a user interface issue what to do when an IRI is
>> encountered that includes that latter.  If I understand you
>> correctly, that behavior is currently undefined in idnabis.
> Yes, that is a problem with the IRI spec.

Put differently, to the extent to which IRIs specify a user
interface behavior, it would be perfectly reasonable for the IRI
spec to specify that SHARP S should be mapped to some other
character or character sequence ("ss" by the orthography rules
of some German-speaking countries, "fs" by appearance, "ſs"
(U+017F U+0073) by origin, etc.   Certainly, if it is to be
mapped to anything but itself, that needs to be specified.  But
it should not be an IDNA problem, especially since IRIs might
choose to map it differently in different contexts (I don't need
to remind either of you that tails are case-sensitive so the
IDNA2003 rules don't apply).


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