Why doesn't Ideographic (ID) in UAX#14 have half-width katakana?

Philippe Verdy verdy_p at wanadoo.fr
Tue Apr 28 03:03:14 CDT 2015

Note: is it really allowed to break between a Latin letter and an
half-width kana? Such sequences are frequent when there are untranslated
foreign Latin (or may be Greek/Cyrillic/Hebrew/Arabic) insertions in
Japanese (toponyms, trademarks, people names...), that are followed by a
semantic kana terminator.
If you allow this break, the terminator will loose its semantic.
There are probably similar exception between [ideographs or fullwidth
Latin/Greek/Cyrillic] and [half-width or full-width kana], for those script

2015-04-28 9:47 GMT+02:00 Philippe Verdy <verdy_p at wanadoo.fr>:

> My feeeling is that half-width kanas behave like Latin letters and do not
> even have to follow the ideographic composition square to line up with them
> (unlike standard kanas). So effectively their line breaking behavior is
> very different.
> Those "half-width letters" are in fact similar to linear jamos (not
> composed into syllabic squares) in the Korean script, and to Bopomofo
> letters. And may be we could add the CJK key letters (radicals used for
> example in IDS) to this list, or Yi radicals.
> They are harmonized to be used along with other alphabetic scripts. In
> fact they may even not be really "half-width" but proportional. They are
> also used with non-ideographic punctuation (notably the ASCII punctuation)
> and standard SPACE (U+0020).
> If rendered in vertical lines, they could be either rotated (just like
> Latin letters), or not (aligned horizontallly like letters in columns of
> crosswords, but they may also have proportional height, like in
> Latin/Greek/Cyrillic where it is sometimes needed for example with capital
> letters with stacked accents, or when using sized spaces)
> So IMHO, those "half-width" letters are in fact to be considered as
> another separate script, for typographic purpose. They are "unified" with
> non-halfwidth letters, only for collation with minor differences
> (plain-text searching and sorting).
> 2015-04-28 4:20 GMT+02:00 Makoto Kato <m_kato at ga2.so-net.ne.jp>:
>> Hi.
>> http://www.unicode.org/reports/tr14/proposed.html#ID defines Ideographic
>> (ID).  Although full-width katakana is included in ID, half-width
>> katakana (U+FF66 and U+FF71-U+FF9D) isn't.  Why?
>> Also, Conditional Japanese Starter (CJ,
>> http://www.unicode.org/reports/tr14/proposed.html#CJ) considers
>> half-width variants such as half-width katakana letter small a.
>> -- Makoto
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