Mappings - some examples

Mark Davis ☕ mark at
Mon Nov 30 19:01:26 CET 2009

Even for English, IDNA does not permit all valid words: "Joe's Bar" will not
work, because of both the space and the apostrophe and "Joe'sBar" because of
the apostrophe. IDNA2008 explicitly does not permit all sequences that would
be valid words in all languages; nor could it do otherwise.

There are two compatibility problems:

   1. Existing web pages and other documents that contain ß and expect to go
   to location X and not Y.
   2. There is still an existing body of billions of browsers that will take
   years to disappear (as Erik points out, something like 20% of browsers are
   still IE6).

Let's suppose that IDNA2008 allows ß, and that the newer browsers use it
(and not a compatibility scheme like The
only real purpose to allowing ß is so that you can distinguish from ss. But
what happens when Herr Stosser gets and Herr Stoßer gets
stoß <>?

Initially, 100% of all browsers will go to the ss form. Nobody will go to
Stoßer's site; his email won't work, etc.: href="stoß<>"
goes directly to "". Even on Stoßer's site, absolute intrapage
links will go to the 'wrong' place. After a while, some newer browsers will
take page href="stoß <>" and go to
while all the other browsers will go to href="". The same goes for
email. So access to all of those links (and mail, etc.) will be unreliable,
and the subject of security and compatibility problems. As a result,
practically, people would be unable to use href="stoß<>"
in their web pages or in email until essentially all existing browsers were
supplanted, which will be maybe 5 years down the line. And during that time,
these will also bollux up all the search engines, since indexing assumes
that links don't have ambiguous targets.

And that assumes that nobody does use a compatibility mechanism. Another,
more likely, alternative based on our conversations with vendors is that
people disregard that part of IDNA2008, and use a compatibility mechanism
like; that allows the browsers, emailers,
search engines and others to keep functioning correctly - there is no
transition. The downside is that you can't register both and
stoß <>. So of the thousand Herr Stoßers, instead of
one of them getting that name, none of them do; it's like "Joe'sBar". And,
of course, there is the disadvantage of having UTS46 have to exist in the
first place.

The third alternative is the really awful one: the "let a thousand flowers
bloom" scenario. In this scenario, there is no single compatibility
mechanism like; instead, we get different
variants from different vendors, and the situation is chaotic. That is the
scenario that the Unicode consortium's members are really concerned with.
While the ideal solution would be an IDNA2008 that maintained compatibility
with IDNA2003, the second best solution is only one compatibility mechanism;
not dozens.


On Mon, Nov 30, 2009 at 07:55, Georg Ochsner <g.ochsner at>wrote:

> > -----Ursprüngliche Nachricht-----
> > Von: idna-update-bounces at [mailto:idna-update-
> > bounces at] Im Auftrag von Alexander Mayrhofer
> > Gesendet: Montag, 30. November 2009 15:57
> > > I would though be more "on your side" if the number of domain
> > > names that contained ß where say 100 times higher than today
> > > in published documents. Because then people would be TOLD to
> > > type in something (ß) that mapped to something else (ss) that
> > > was registered. That, I claim, is not the case. At least not
> > > "heavily".
> >
> > I understand that. And i'm saying that the potential of around 500
> > useful "ß" registrations (based on looking through our inventory of 900k
> > domains) is by far not worth the effort.
> In several talks with people from the Austrian registry I've now heard this
> argument. But I think this decision should not be made depending on
> commercial factors. IDNA is in my eyes not a question of return on
> investment but about the native use of language in domain names around the
> globe. Once more, the Austrian registry can still refuse to have sharp s
> registered within their namespace, but maybe other registries pay more
> attention to the language aspect than to commercial calculations.
> Best regards
> Georg
> _______________________________________________
> Idna-update mailing list
> Idna-update at
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