Re: Tamil 0BB3 and 0BD7

From: Philippe Verdy (
Date: Mon Nov 10 2003 - 04:47:06 EST

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    From: "Peter Jacobi" <>
    To: <>
    Sent: Monday, November 10, 2003 9:51 AM
    Subject: Re: Tamil 0BB3 and 0BD7

    > Hi Doug, All,
    > "Doug Ewell" <> wrote:
    > > [..] Second, disunifying "y"
    > > would cause untold mapping nightmares. [..]
    > Not exactly nightmares, but the Tamil case does
    > cause some mapping discomfort.
    > About three out of five 7bit/8bit encodings for Tamil
    > have these two Unicode codepoints unified. And at
    > least one of the dis-unified ones did the dis-unification
    > exactly for Unicode interoperability.

    So it remains at least one of these encodings where
    the characters were disunified.

    This should have been solved in Unicode by creating
    a compatibility equivalent (so that bijective mapping
    with this encoding remains possible), but with a
    compatibility decomposition to the other code point
    (like for CJK compatibility ideographs that had two
    position assignments in legacy encodings).

    > So in effect, Unicode handling of this case, may actually
    > change Tamil use - I've already seen proposals to
    > a script reform dis-unifying the glyphs.

    I bet that the AU length mark should have been this
    compatibility assignment in Unicode, because the same
    letter can be treated individually as a base character, and
    should prevail to the combining interpretation which is
    language-specific and contextual, butnot needed for the
    correct rendering of Tamil.

    But yes, this separation in code points will have the effect
    of users wanting to create glyph variant for the AU length
    mark, finally splitting the usage of the letter the same way
    as it occured in Latin between U and V, simply because it
    allowed easier reading by removing the required contextual
    analysis of the written glyph.

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