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Re: New Internet Draft on registering IDNs
tedd <tedd@xxxxxxxxxxxx> wrote:
> But please note that every glyph that looks like "A" has also been
> mapped to 0061 (a). For example, from the newer Unicode Mathematical
> Alphanumeric Symbols table every "A" (1D400 to 1D670 ) has been mapped
> to 0061 (a) as well.
Those are not merely things that look like A, they are all in fact
instances of the letter A. That's why they are mapped.
Things that merely look like A are not mapped. Stephane gave one
> For instance, the Greek capital Alpha U+0391 cannot be distinguished
> visually from a Latin capital A but is not mapped to A by nameprep.
There is another example in the Cyrillic alphabet.
By the way, the IDN folks are responsible for none of the mappings in
Nameprep except the few map-to-nothing rules. All other mappings were
simply imported from the Unicode Consortium. The normalization mappings
are designed to coalesce alternate representations of the same text,
while the case-folding mappings are designed to coalesce strings that
differ only in the upper/lower case of letters. Neither set of mappings
is designed to coalesce strings that are visually similar.