Confusability (Re: New version, draft-faltstrom-idnabis-tables-02.txt, available)

Gervase Markham gerv at
Mon Jun 18 13:06:21 CEST 2007

John C Klensin wrote:
> * One key reason why underscore was excluded from the
> letter-digit-hyphen hostname rule was because, when written with
> a pen, it was too easily confused with hyphen.  As Mark Andrews
> suggests, symbols were excluded at the same time because they
> didn't reliably and consistently appear on keyboards and because
> there is no consistent, predictable, worldwide terminology for
> most of them, despite the terms chosen in Unicode.  

And this, incidentally, is one good reason why the chap whose email just 
came through who bought www.<peace sign>.com as a speculator was sadly 
misguided. How is anyone going to type that? Or talk about it in a way 
which doesn't confuse it with

> * We've got a similar problem with IPA.  The first version of
> the tables document excluded the IPA block entirely.  As Harald
> mentioned, that resulted in two strong criticisms.  One was that
> many of the characters had been adopted into African languages
> and (presumably because there were no extant national or
> international standards that were specific to those languages)
> the IPA characters had to be used if reasonable mnemonics were
> to be constructed based on words of those languages.  The other
> was that we should refrain from writing rules based on character
> blocks, rather than on property lists.   So now we have IPA back
> in, which cases problems with IPA characters that are basically
> font variations on basic Latin ones.  It is clear to me (at
> least) that we can't have any font variations in the
> IDN-permitted set and, indeed, that such variations must be
> forever excluded if we are not to have major problems. 

It isn't clear to me that we must exclude these. Like Greek omicron and 
Latin o, assuming that these "font variations" are in fact characters in 
someone's written language, can't we include them and sort the 
confusable problem out at a higher level?


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