Unicode 5.2 -> 6.0

Gervase Markham gerv at mozilla.org
Fri Oct 15 10:59:00 CEST 2010

On 14/10/10 23:08, Kenneth Whistler wrote:
> Furthermore, the main community which is concerned with
> the New Tai Lue script is in a very remote prefecture
> in Yunnan Province in China:
> http://en.wikipedia.org/wiki/Xishuangbanna_Dai_Autonomous_Prefecture
> It would be very difficult to find out what that community
> may *already* be doing with the New Tai Lue encoding,
> for IDNs or anything else. Certainly I wouldn't bet on
> no one among the nearly a million residents from  being
> able to render U+19CA.

Let me see if I understand this:

- There is a character added to Unicode in 5.0/5.2, which was not valid 
in IDNA2003.

- For a short time, it was valid in IDNA2008.

- It was never registerable in any of the top-level domains who use a 
character whitelist (as far as I know).

- It was never renderable in Firefox (as no registry on the whitelist 
included it). It may have been renderable in other browsers if they had 
updated their code to IDNA2008 to allow it (which I don't think anyone 
has done yet), if their language-related or registry-related policies 
allowed it, and if the person viewing the address had a font installed 
including it. But I think it's most likely that no browser could display it.

(Yes, browsers are not the only means of displaying domain names.)

And now, we are concerned that someone in the Xishuangbanna Dai 
Autonomous Prefecture, or someone with business there, might have, in 
the small time window available, created a DNS entry using this name, 
using some editor to edit their zone file containing a font which can 
display it, and using some client or service which is able to display it 
to their users, and now would be significantly inconvenienced by 
changing it?

This seems unlikely to me. But I guess I don't live there.

The downside is that, for ever more, every IDNA implementation has to 
deal with this exception. Perhaps it's no big deal because the size of 
the exception list will inevitably eventually grow beyond zero, but it 
seems a shame.


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