Tables and contextual rule for Katakana middle dot

Mark Davis mark at
Tue Apr 7 20:29:50 CEST 2009

First off, the Katakana middle dot is distinctive enough that I see no
problem with visual confusion. Take a look at:

a ・

The width and positioning is far different.

There are other dot-like characters that are far more visually similar to
dot, like Arabic zero.

عربي٠عربي.com <>
عربي.عربي.com <>

But more importantly, there is a real lack of data presented for these kinds
of positions. When excluding characters that are in common use on the basis
of visual confusability, such as Katakana middle dot, let's see some real
data on what a difference this would make in overall visual confusability of
characters. Of all of the visually confusable characters in PVALID, what
would be the percentage difference but adding or removing Katakana middle
dot? And why do people think this can't be handled by exactly the same
mechanisms that programs have to handle the visually confusable characters
that *are* PVALID.


2009/4/7 John C Klensin <klensin at>

> --On Tuesday, April 07, 2009 07:59 -0700 Mark Davis
> <mark at> wrote:
> > On what basis?
> It is a punctuation character.  It looks enough like a
> label-separating period in contexts where middle-dots are not
> used that it would likely be mistaken for a period in those
> contexts.  Such a mistake is fully as dangerous as a character
> that looks like a slash.  If it were possible to live with a
> restriction that required at least one Asian-Japanese character
> (Hiragana, Katakana, or Kanji) in the label, I'd be ok with it,
> although a little nervous.  But, if abc・def and 10・0・0・6
> (if one doesn't see the characters, the indicators are U+03FB)
> would be valid labels under the only acceptable rule, then I
> think the middle dot is at high enough risk of causing harm to
> be DISALLOWED entirely.  That saddens me as much as it does
> Harald.
> On the other hand, if the reason for this problem is that
> Romanji is Japanese, then so, I suppose, is hyphen-minus.  I
> would suppose that could be used instead and mapped, as a
> presentation issue, to middle dot were appropriate.   Not a
> wonderful situation, but maybe better than the alternatives.
>   john
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