From: Ernest Cline (ernestcline@mindspring.com)
Date: Sat Apr 10 2004 - 11:33:35 EDT
> [Original Message]
> From: Peter Kirk <peterkirk@qaya.org>
> To: Unicode List <unicode@unicode.org>
> Date: 4/10/2004 12:47:45 PM
> Subject: Variant positions of combining marks
>
> Does anyone know of any cases where the same combining mark is combined
> with the same base character in two or more different positions, and
> where the positioning is semantically significant? How does Unicode deal
> with this situation? Would variation selectors be appropriate in this
> situation, or what other mechanism might be proposed?
>
> I am looking for examples other than Hebrew vav and holam, because
> I am looking for precedents for dealing with this situation elsewhere in
> Unicode. I am also excluding distinctions like DOT ABOVE and DOT
> BELOW, where the marks are treated as different characters although
> the glyphs may actually be the same.
Since the fixed position of the holam variant under discussion is not the
same as that of holam, a variation selector would definitely not be
appropriate. Holam has canonical combining class 19, and as such
any variant identified by a variation selector would be of that class and
should therefore place its mark in the same fixed position as holam.
The shin dot and sin dot pair applied to the letter shin is probably the
closest analogy. Same base character, with identical looking marks
distinguished by position only and having different fixed position
canonical combining classes. That suggests that if the holam variant
that is under discussion is accepted for Unicode, then it should be
encoded as a separate character with a fixed position combining
class other than 19. If one of the other fixed position classes used by
Hebrew (Hebrew uses the range 10-26) is not identical to the position
of this variant, then a new class will need to be added, perhaps class
37 as that is the closest unused fixed position canonical combining
class to the existing Hebrew classes.
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