Re: What is the principle?

From: Philippe Verdy (
Date: Wed Mar 31 2004 - 02:37:03 EST

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    From: "Kenneth Whistler" <>
    > Consider another example. The normalization algorithm has to work
    > for *all* Unicode code points, assigned or not, because it guarantees
    > stability into the future when characters are encoded at code points
    > which were previously unencoded. It also, then, obviously has to
    > work for PUA characters, as well. That implies that two additional
    > properties *MUST* have some default values set for PUA characters.
    > One of those is decomposition, which is defaulted to the null string
    > (no decomposition) for all PUA characters. The other is canonical
    > combining class, which is defaulted to ccc=0 for all PUA characters.
    > Doing anything else would have just been stupid. But again,
    > "None of the Above" was not an option.

    All these arguments are in favor of a definition for default properties set with
    reasonnable values that match the most common (?) needs. Still this should not
    prohibit the use and interchange of other properties. and these defaults are
    then not mandatory and are overridable.
    Even in the case of an API that requires being able to do something like:
    Character(E000).getProperty(), that API may be prefeeded with a table of
    properties override for PUAs.

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