Re: IDN and Missed Normalisations

From: Mike (
Date: Mon May 07 2007 - 16:45:59 CDT

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    Philippe Verdy wrote:
    > Richard Wordingham wrote:
    >> The present standard for International Domain Name Processing (nameprep -
    >> RFC 3491 and stringprep - RFC 3454) currently operates with four steps:
    >> mapping, normalisation (NFKC), prohibition and bidi checking. Mapping
    >> replaces single characters by sequences, which may be empty. It is
    >> composed
    >> of two elements - deletion of default ignorables, and full case-folding,
    >> complicated because it is done before compatibility decomposition. (I may
    >> have missed some minor wrinkles in mapping.)
    > Isn't the Unicode normalization the first step to perform before performing
    > mappings and deletion?

    No, there are two possible mappings: one for when you plan to normalize
    and the other when you are not normalizing. NFKC is the second step, if
    the stringprep profile requests it, as does nameprep.


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