L2/04-124
From: Mark Davis
Subject: Script Values
Date: April 6, 2004

1. In 4.0.1 we added a new script value:

3031..3035    ; Katakana_Or_Hiragana # Lm   [5] VERTICAL KANA REPEAT
MARK..VERTICAL KANA REPEAT MARK LOWER HALF
309B..309C    ; Katakana_Or_Hiragana # Sk   [2] KATAKANA-HIRAGANA VOICED SOUND
MARK..KATAKANA-HIRAGANA SEMI-VOICED SOUND MARK
FF70          ; Katakana_Or_Hiragana # Lm       HALFWIDTH KATAKANA-HIRAGANA
PROLONGED SOUND MARK
FF9E..FF9F    ; Katakana_Or_Hiragana # Lm   [2] HALFWIDTH KATAKANA VOICED SOUND
MARK..HALFWIDTH KATAKANA SEMI-VOICED SOUND MARK

A. It appears that we missed some other characters that should have an explicit
value:

Proposed:
30FC          ; Katakana_Or_Hiragana # Lm       KATAKANA-HIRAGANA PROLONGED
SOUND MARK

Maybe also:

30A0          ; Katakana_Or_Hiragana # Pd       KATAKANA-HIRAGANA DOUBLE HYPHEN

30FB          ; Katakana # Pc       KATAKANA MIDDLE DOT
FF65          ; Katakana # Pc       HALFWIDTH KATAKANA MIDDLE DOT


B. We should have also updated the list in TR #29, which currently reads:

Katakana: Script = KATAKANA, or
Any of the following:
U+30FC (ー) KATAKANA-HIRAGANA PROLONGED SOUND MARK
U+FF70 (ｰ) HALFWIDTH KATAKANA-HIRAGANA PROLONGED SOUND MARK
U+FF9E (ﾞ) HALFWIDTH KATAKANA VOICED SOUND MARK
U+FF9F (ﾟ) HALFWIDTH KATAKANA SEMI-VOICED SOUND MARK

If the above Script changes are made, then it would be changed to simply:

Katakana: Script = Katakana, or Script = Katakana_Or_Hiragana

(Since Katakana_Or_Hiragana characters typically follow a base, it is no problem
that the rule will cause no breakage between them.)

2. Right now, people have to dig the definition of the properties out of the TR.
It would be better both for them and for our maintenance if they were treated
like Line Break, as enumerated properties, with the values as given by TR #29
(as amended by the above). Here are suggested names.

Default_Grapheme_Cluster_Type (DGCT)
Default_Word_Type (DWT)
Default_Sentence_Type (DST)

The "Default" is explicit in the name, so that people are clear that these are
expected to be overridden.

Mark