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

suzuki toshiya mpsuzuki at hiroshima-u.ac.jp
Fri May 1 10:25:24 CDT 2015

Dear Ken,

Ken Whistler wrote:
> The other thing that I think would need to happen here is that any proposal
> should also provide suggested wording for UAX #14 which would explain
> why halfwidth katakana specifically need to break with the general 
> principles
> that were used 15 years ago to assign LB classes based on East_Asian_Width
> considerations, and instead need to match the LB classes of their
> fullwidth katakana counterparts. That should be made explicit in the text
> of UAX #14, so somebody else doesn't "discover" another inconsistency
> between sets of values and try to change things back later on -- not 
> knowing
> the rationale for the values.

Excuse me, there is any discussion record how UAX#14 class for
halfwidth-katakana in 15 years ago? If there is such, I want to
see a sample text (of halfwidth-katakana) and expected layout
result for it.

You commented that the UAX#14 class should not be changed but
the tailoring of the line breaking behaviour would solve
the problem (as Firefox and IE11 did). However, some developers
may wonder "there might be a reason why UTC put halfwidth-katakana
to AL - without understanding it, we could not determine whether
the proposed tailoring should be enabled always, or enabled
only for a specific environment (e.g. locale, surrounding text)".

If UTC can supply the "expected layout result for halfwidth-
katakana (used to define the class in current UAX#14)", it
would be helpful for the developers to evaluate the proposed
tailoring algorithm.


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