The real issue: interopability, and a proposal (Was: Consensus Call on Latin Sharp S and Greek Final Sigma)

Mark Davis ☕ mark at
Tue Dec 1 18:04:47 CET 2009

To be complete, one would ban mapping not only of PVALID, but also of
DISALLOWED (since those are in an indeterminate state, and could become


On Tue, Dec 1, 2009 at 05:22, Vint Cerf <vint at> wrote:

> As john klensin has pointed out no mapping of pvalid chars has always been
> an intent of idnabis and there was even text to that effect I think. It is
> a
> good organizing principle
> ----- Original Message -----
> From: Alexander Mayrhofer <alexander.mayrhofer at>
> To: Patrik Fältström <patrik at>; Shawn Steele
> <Shawn.Steele at>
> Cc: Harald Alvestrand <harald at>; idna-update at
> <idna-update at>; lisa Dusseault <lisa.dusseault at>;
> Mark
> Davis ☕ <mark at>; "Martin J. Dürst" <duerst at>;
> Vint Cerf <vint at>
> Sent: Tue Dec 01 04:59:54 2009
> Subject: The real issue: interopability, and a proposal (Was: Consensus
> Call
> on Latin Sharp S and Greek Final Sigma)
> (I've spent quite some time on re-thinking the issue last night. It's a bit
> longish, and the promised proposal is at the end).
> I think i didn't make it clear enough in my previous messages that i'm not
> an opponent of the character Latin Sharp S itself. I'm opposing against
> changes that have a high risk of introducing interopability, particularly
> in
> the long run.
> My *only* major concern is that the introduction of the Latin Sharp S is
> exactly such a case, but a particularly nasty one. I understand that the
> majority of WG participants think that "ß" should be PVALID (i'm carefully
> avoiding the word "concensus" here, because it's obviously up to the WG
> chair to declare that).
> If i look at the issue in an isolated way, not considering any
> compatibility/interopability issues, then it makes perfectly sense to
> declare "ß" PVALID, because (this is sort of convincing myself here ;) :
> - There seems to be little existing deployment of ß-labels out there, at
> least on the web - the client side is a different issue, there's nearly
> 100%
> deployment. We can also err guesstimate that "ß" has only about 1% of the
> deployment of other german "umlauts", according to Erik's numbers (As Eric
> pointed out, those numbers have no indication of confidence, though). We
> don't know how many people type "ß" into their browser address bar, though,
> which is at least "unsatisfying" from an engineering perspective.
> - The character is undoubtly part of German grammar, at least in two of the
> three countries where German is an official language - i don't know about
> the minorities in other countries. The upper case variant as well as the
> Unicode casing and folding is.. well, extravagant - but the lowercase "ß"
> is
> definitely part of the grammar.
> - Georg's argument that this would be "the last chance" to introduce "ß",
> got me thinking. If the "Exceptions" would be implemented as an IANA
> registry, it would be much easier to add (and probably remove) characters.
> But given that changes to the Exceptions now require an update to the base
> specification, we should probably take this opportunity, rather than
> waiting
> for IDNA2015.
> So, as i said multiple times, the problem is changing the semantics of a
> part of the namespace, definitely from the user's perspective - one could
> argue whether or not that means the "protocol semantics" change, since the
> mapping step ist part of the protocol of IDNA2003.
> Regarding interopability, i'm not so much concerned about the transition
> period between IDNA2003 and IDNAbis. This will be painful, but it will be
> (hopefully temporary).
> What i am more concerned is that the legacy of the "ß-ss" mapping would
> introduce incompatibility for an indefinite period of time, *after* all
> clients have switched over to IDNAbis. This could happen because some
> vendors would implement mappings to be fully IDNA2003 backwards compatible,
> and others would implements the informative idnabis-mappings only.
> From a registry point of view, i would very much like to avoid any
> bundling.
> However, the "permanent" interopability issues outlined above are bound to
> "taint" labels with an "ß" for an indefinite period of time, with the most
> sensible option to disallow registration completely to avoid those
> problems.
> I think it's not very likely that all vendors agree on a single mapping -
> particularly with the WG scope of not dealing with a mapping as part of the
> protocol. However, i'd like to propose the following:
> - add text to Section 5 of idnabis-protocol that says
>        "characters that are PVALID MUST NOT be subject to mappings".
> Or (more focused)
>        "characters that are listed as Exceptions (F) in Section 2.6
>         of [tables] MUST NOT be subject to mappings"
> I'm not sure whether that contradicts the "local matters" part in Section
> 5.1 (and i'm pretty sure it creates problems elsewhere), but i think it
> solves the "permanent interopability" problem outlined above. That means
> that "ß" stops working during the transition period, but also means that it
> can be treated as an independent character *after* the transition -
> bundling
> is not required, Mr Weiss and Mr Weiß can both have their distinct domain
> names, etc..
> Is that a way forward? Comments appreciated.
> Alex
> _______________________________________________
> Idna-update mailing list
> Idna-update at
-------------- next part --------------
An HTML attachment was scrubbed...

More information about the Idna-update mailing list