Final Sigma (was: RE: Esszett, Final Sigma, ZWJ and ZWNJ)

Erik van der Poel erikv at google.com
Fri Feb 27 06:53:51 CET 2009


Hi John,

The idea was not a fully fleshed out proposal, as I'm sure most people
are aware. I have no idea whether we can add any more "fields" (for
lack of a better term) to the relevant part of the DNS, but I was
simply imagining that one could add a new, optional field that would
only serve as a hint to the software that is attempting to decode the
Punycode and display the resulting Unicode on some device. In the
absence of the hint, the software would simply display the Unicode as
is, i.e. in the case of Greek, probably lower-case characters without
tonos, and normal, lower-case sigma instead of final sigma. If the
software was able to retrieve the hint for a particular label (if not
FQDN), the hint would indicate which characters should have a tonos,
and which sigmas should be final.

I certainly do not want to give anybody the impression that fields can
be added to DNS willy-nilly. Such endeavors must be carefully
considered, preferably by DNS experts. :-)

You're probably right that one of the original goals of IDNA was to
avoid "changes" to DNS itself, but given that one can retrieve e.g. A
for IPv4 and AAAA for IPv6, I don't consider it so outrageous to store
yet another piece of info about a label (or FQDN) in the DNS.

If people outside Greece want to use Greek characters but don't mind
the way IDNA2003 maps sigmas (and doesn't map characters with tonos),
then they could of course just use IDNA2003 with xn--. One of the
difficulties with this idea is to come up with a clean way for an
implementation to decide which mapping spec and prefix to use (xn-- vs
xo--) when the user is typing the label on the keyboard (given that
labels inside e.g. HTML files would always be processed the IDNA2003
way). One very simple and probably silly idea is: if the label is
being typed on the keyboard, and if the TLD is .com, then use IDNA2003
with xn--. If the TLD is .gr, then use the new Greek mapping spec with
xo--.

Does this explain my thinking a bit better? Again, I don't really want
to go down this path because of the difficulties of multiple prefixes.

I apologize for sending out half-baked ideas. I was only wondering
what we might be able to do for the Greeks, other than DNAME or a new
*NAME that actually solves their problem neatly.

Erik

On Thu, Feb 26, 2009 at 7:45 PM, John C Klensin <klensin at jck.com> wrote:
>
>
> --On Wednesday, February 25, 2009 09:48 -0800 Erik van der Poel
> <erikv at google.com> wrote:
>
>>...
>> Then there could be an extra field in the DNS that indicates
>> how to display those names in Unicode form. I.e. it would tell
>> you which sigmas are supposed to be final, which characters
>> should have a tonos, and so on.
>>...
>
> Erik,
>
> Could you please explain "extra field in the DNS" to those of us
> who are under the impression that
>
>        * that there are no places to put extra fields in any RR
>        type in CLASS IN
>
>        and/or
>
>        * that the primary premise of IDNA is to avoid making
>        any changes to the DNS.
>
> ... just trying to understand what you are proposing.
>
> I hope it is not to encourage Greece to do something that would
> not be interoperable with the rest of the Internet, including
> people outside Greece that are using Greek characters?  That
> would rather defeat one of the advantages of IDNs as well as
> having other bad consequences.
>
> best,
>     john
>
>


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