Re: What is the principle?

From: Ernest Cline (
Date: Wed Mar 31 2004 - 18:32:48 EST

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    > [Original Message]
    > From: Peter Kirk <>
    > Ernest, I support your general ideas here. But I am concerned about the
    > implications of defining PUA characters with combining classes other
    > than zero. I can see this causing some confusion with normalisation etc.
    > And it does hugely multiply the number of PUA characters required.
    > <snip>
    > Is it really necessary to support to this level of detail the concept of
    > canonical equivalence of PUA sequences?

    If you want them to be able to interact with the existing combining marks
    then any proposal for more specific private use characters will need to
    include combining characters for every existing combining class. 128
    characters per class may prove to be overly generous, but it serves
    as a starting point for discussion. The number was chosen because
    of the stated preference of assigning character blocks that line up
    in groups of 128. A detailed proposal would definitely need to examine
    existing scripts as it would be wasteful to assign too many yet pointless
    to assign too few. I can't see any useful proposal for more specific
    Private Use characters as using less than half a plane. Any proposal
    that uses more than one plane will need a lot of justifying to have any
    chance, and even with ten unspoken planes out there, Any proposal
    that would call for more than two planes will not go anywhere.

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