Re: Defined Private Use was: SSP default ignorable characters

From: Philippe Verdy (
Date: Thu Apr 29 2004 - 10:29:42 EDT

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    ----- Original Message -----
    From: "C J Fynn" <>
    To: "Unicode List" <>
    Cc: "Philippe Verdy" <>
    Sent: Thursday, April 29, 2004 1:39 PM
    Subject: Re: Defined Private Use was: SSP default ignorable characters

    > "Philippe Verdy" <> wrote:
    > > a font made for PUAs will also deliver at least a
    > > definition URI record. The actual character properties tables need not be
    > > present within the font itself.
    > It is possible to embed a URI in a font - there are already places to embed
    > designer, vendor and licence URL's in a font. However remember that in
    > developing countries, where some lesser used scripts which might have only a
    > PUA encoding may be used, connection to the internet may be a problem. It is
    > just as easy to embed a table of character properties in a font as it is to
    > embed a URL.
    > TrueType, AAT, OpenType and Graphite fonts all have an extensible table
    > structure so there are no technical difficulties to adding such a table. Of
    > course the name for a table which embeds character properties (or a URL
    > pointing to a properties table) must not conflict with existing table names.

    Certainly, but what is the distinction between downloading/distributing a font
    or downloading/ditributing a XML file containing the PUA conventions?

    Someone argued that a font was not the best place to embed these conventions,
    and they are probably right. But tagging a font by embedded a list of
    PUA-conventions URIs that it supports is not impossible, and even wishable if
    the font is made mostly for PUAs with scripts still unsupported by Unicode or in
    a experimental status.

    As soon as one recognizes that a private agreement must be made to use any PUA,
    it seems reasonnable to think about a way to assert that such private convention
    exists and to which rules and character properties it corresponds. Having a
    concrete syntax to transport such conventions would still be a useful tool to
    allow users use their PUA the way they want. This is separate from the syntax of
    the signature URI to embed in documents or fonts or whatever data structures
    that will recognize and handle this convention.

    So an URI (I did not say "URL" and not even a URL on the Internet) seems
    reasonnable and offers no limitation on the way the private conventions will be
    transported and agreed upon by private users. You even don't need any Internet
    access to use a URI: it may simply be a UUID as well, easy to create locally...
    Users choose then the URIs they will want to support...

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