RE: Normalisation stability, was: Compression through normalization

From: Philippe Verdy (
Date: Tue Nov 25 2003 - 10:22:26 EST

  • Next message: Peter Kirk: "Re: Normalisation stability, was: Compression through normalization"

    > >So it's the absence of stability which would make impossible this
    > >rearrangement of normalization forms...
    > Canonical equivalence is unaffected if combining classes are rearranged,
    > though not if they are split or joined. It is only the normalised forms
    > of strings which may be changed. So this is no argument against
    > rearranging combining classes.

    Note that I did not want to speak about the relative order of combining
    classes, but to the existence of canonical decompositions or composition
    exclusions, and that's where we were speaking when comparing the merit of
    composed and decomposed forms for compressability.

    The most important part of the stability policy is the one that recognizes
    that any two strings are or are not canonically equivalent (so splitting or
    merging classes is denied, as well as adding or changing or removing
    decompositions of characters already assigned in the UCD). It is this part
    of the policy that allows rearrangement of strings by various normalized

    Composition exclusions have a lower impact as well as the relative orders of
    canonical classes, as they don't affect canonical equivalence of strings,
    and thus won't affect applications based on the Unicode C10 definition; they
    are important only to allow binary compares of normalized strings.

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