Unicode & IETF

John C Klensin klensin at jck.com
Wed Aug 13 02:48:54 CEST 2014

--On Tuesday, August 12, 2014 14:44 -0400 Vint Cerf
<vint at google.com> wrote:

> Isn't it the case that NFC does NOT convert sharp-s to ss or
> vice versa? assuming that is correct, then these are treated
> as distinct,  at least for comparison purposes.

No, but CaseFold does because it essentially
   converts everything to upper case  then
   converts everything back to lower case

It is also subject to stability rules, so the relatively recent
addition of upper case sharp-s didn't help.   Since there was no
upper case form, the conversion to upper case turns ß (U+00DF)
into "SS" and then converting that to lower case produces "ss".  

That is one reason IDNA2008 does not perform case folding

And, once again, Shawn, unless you look at "ß" and see "ss",
the relationship is an interesting topic but not relevant to the
current thread, nor is any resemblance you might see between
"ß" and "β" (U+03B2).  Even if they did look the same to you,
it might not be relevant unless, e.g., they occupied the same
key on your keyboard.  As far as I know, no one is trying to get
a universal similar-looking character recognizer out of these


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