Re: What is the principle?

From: Ernest Cline (
Date: Sun Mar 28 2004 - 00:11:28 EST

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    > [Original Message]
    > From: <>
    > Asmus Freytag wrote,
    > > Uninterpreted VS characters should *not* turn into black blobs. If we
    > > wanted that to happen, we would have coded different characters.
    > U+E000 COMBINING BLACK BLOB? Censors would probably love it.
    > > >What does the collation standard say to do with unassigned codepoints
    > > >anyhow?
    > >
    > > Variation selectors are not unassigned characters.
    > But, they might be regarded as such by any application predating VSs.
    > likewise for any VS sequences approved after the application was created.

    For a an application that predates the addition of that Variation Selector
    character yes, but not for an unrecognized variation selector sequence.
    The standard is quite clear that if a Variation Selector is recognized, but
    the sequence it is, then it should be treated the same as if no selector was

    This is one reason why transferring some or all of the Variation Selectors
    on the SSP to Private Use is a possibility if they are not going to have
    any official uses. Any Unicode 4.0 compliant software would
    degrade the presentation of such data gracefully.

    The only reason I can see for having 256 Variation Selectors is to
    enable round trip encoding of data using legacy 8 bit character sets
    that has data which is either invalid or unknown in Unicode. Then
    either U+001A or U+FFFD followed by a variation selector could be
    used to record the original octet for the round trip. Freeing up the
    240 SSP variation selectors for private use except for a few defined
    algorithmic uses such as this would seem to make sense I find it
    doubtful that any non-algorithmic uses of Variation Selectors will
    require even as many as 16 such selectors for official sequences.

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