Re: RE: IPA Null Consonant

From: Jim Allan (
Date: Mon Jun 02 2003 - 17:21:33 EDT

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    Rick McGowan asked:

    > Can someone point more specifically to where it says anything about
    > variation selectors? This pointer is to the table of contents/overview...

    Well, at
       I find:

    << This specification of MathML makes use of some characters that are
    not part of Unicode 3.0 but which have been proposed to the Unicode
    Technical Committee (UTC), and thus for inclusion in ISO 10646. They are
    presently expected to be in the revisions Unicode 3.1 and 3.2. (For more
    detail about this see Section 6.4.4 [Status of Character Encodings].)

    While the process of review and adoption by UTC and ISO/IEC of the
    characters of special interest to mathematics and MathML is largely
    complete (Unicode Work in Progress) there remains the possibility of
    some further modification of the lists of characters accepted, of the
    code assignments for those adopted, or of the names given them by
    Unicode. To make sure any possible corrections to relevant standards are
    taken into account, and for the latest character tables and font
    information, see the W3C Math Working Group home page and the Unicode
    site. >>

    This indicates we are dealing with a fairly old and tentative


    << 6.3.5 Variant Mathematical Characters

    Unicode attempts to avoid having several character codes for simple font
    variants. For a code point to be assigned there should be more than a
    nuance in glyphs to be recorded. To record variants worth noting there
    is a special character proposed for Unicode 3.2, U+FE00 (VARIATION
    SELECTOR-1), which acts as a postfix modifier. However the legally
    allowed combinations with this variation selector are restricted to a
    list recorded as part of Unicode. The VARIATION SELECTOR-1 character may
    only be applied to the characters listed here. The resulting combination
    is not regarded by Unicode as a separate character, but a variation on
    the base character. Unicode aware systems may render the combination as
    the base if the available fonts do not support the variant glyph shape. >>

    At the bottom of the page:

    << The additions accepted are expected to be published as an amendment
    to [ISO/IEC 10646-1], and to become part of Unicode 3.2. It can
    therefore be expected that almost all of the characters in this category
    will finally be accepted, and encoded at the current code points. It is
    possible that a small number of characters may be renamed, moved, or
    less likely, ultimately rejected. There is even a handful of characters
    which have still Private Use Area codes in our tables; even these it is
    hoped will finally be fully recognized. Until final acceptance,
    implementers and users of MathML are using these characters and code
    points at their own risk. Entities and the mathvariant attribute are
    used to avoid that risk. >>

    Variants that are part of the recommendation appear at
    including the slashed zero glyph.

    It would seem that the slashed zero variant was either not actually
    included in the variants eventually proposed or was not accepted or
    (barely possible) was somehow lost and forgotten about.

    But the recommendation is quite clear about the tentative nature of its

    Jim Allan

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