Re: GB 18030 Certification

From: Andrew West (
Date: Fri Aug 19 2005 - 07:30:43 CDT

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    On 19/08/05, Christopher Fynn <> wrote:
    > Patrick Andries wrote:
    > > Does the GB 10840 Certfication require that Chinese Minority scripts be
    > > displayed properly (i.e Mongolian or Tibetan) ?
    > >
    > For a higher level of compliance you will now have to be able to
    > properly display ligatures for a sub-set of about 1500 Tibetan
    > combinations ("Set A" used in modern publications)
    > For the highest (A+) level of compliance you will have to be able to
    > properly display proper ligatures for an additional set of over 5,500
    > Tibetan combinations ( ("Tibetan Set B" additional combinations found in
    > tradtional Tibetan texts).
    > This is further complicated since in some Chinese encodings and systems
    > they seem to use the combintatons (ligature gyphs) in their Tibetan sets
    > A and B as (pre-composed composite) *characters* mapped to fixed
    > Unicode PUA and supplementary PUA code points. While this avoids the
    > need for OpenType or similar shaping to properly dsplay Tibetan text it
    > means that text needs to be converted to (de-composed) Unicode for other
    > systems.

    Text only needs to be converted from precomposed Tibetan in the PUA to
    standard Unicode Tibetan if you need to process the data using tools
    designed to work with standard Unicode Tibetan, or if you need to
    collate or merge such text with standard Unicode Tibetan text. With
    the right fonts precomposed PUA Tibetan should be rendered correctly
    on any system that supports Unicode (excepting Word, as it will
    probably apply unwanted font substitutions on the PUA text), although
    you may not get correct word selection and line break behaviour.
    Incidentally BabelPad already supports conversion between standard
    Unicode Tibetan and the Chinese "Extended Tibetan Set A" in the PUA.

    If support for the Chinese "Set A" set of precomposed Tibetan stacks
    is now a requirement for GB18030 certification, then I would have
    thought that OpenType Tibetan fonts such as Xiamalaya and Tibetan
    Machine Uni that already fully support Unicode Tibetan by means of
    OpenType tables could be made GB18030 compliant by adding in extra
    mappings from the PUA codepoints defined in Set A to the appropriate
    glyphs in the font where available or by decomposing the PUA code
    points using OpenType features. In principle, it should be fairly
    straightforward to support both encoding mechanisms in a single
    OpenType font using a single set of glyphs.


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