Re: Defined Private Use was: SSP default ignorable characters

From: Peter Kirk (
Date: Wed Apr 28 2004 - 16:38:54 EDT

  • Next message: Peter Kirk: "Re: Defined Private Use was: SSP default ignorable characters"

    On 28/04/2004 12:29, Philippe Verdy wrote:

    >From: "Peter Kirk" <>
    >>Software developers, or applications, are not supposed to be party to
    >>the agreement between *users*.
    >Do you say there that software developers are failing to comply with Unicode
    >rules by refusing to develop systems that allow *users* to make such private
    >private agreements and use the PUAs effectively as they are legitimately in
    >right to ask to their software developers?

    No, I have not said this. An implementation which doesn't support the
    PUA at all, or which only supports a few characters defined by itself,
    is compliant. I might say that an implementation which claims to support
    the PUA should do so, at least with the defined default properties,
    independently of any specific agreement between end users.

    >Interesting point. This would be an argument for the developement (out of
    >Unicode) of some standard technical solutions to exchange these private
    >conventions on PUA usage, including exchange of character properties, etc...
    >Why not then within fonts -- namely in Opentype tables for fonts built with
    >these PUA assignments?

    Sounds like a good idea to me. But they are useful only if developers
    choose to implement this mechanism. Unicode cannot and will not oblige
    them to do so.

    >If so, a fully Unicode-compliant system should offer ways to allow interchange
    >of data between parties of these private agreements, and ensure that the PUA
    >encoding conventions are isolated and kept within the domain of the private
    >agreement (for example by labelling documents, with tags containing a URI,
    >either by out of band encoding in rich text formats such as XML or precomposed
    >PDF files, oe either in band within the encoded text using special tags, in a
    >way similar to language tags, but currently Unicode has not defined such an area
    >in plane 14 for other use than just language tags).

    Philippe, I would not dare to propose such a mechanism, although it does
    seem to me to make sense. But again such things, and most of what
    followed in your posting, are useful only if someone chooses to
    implement them.

    Peter Kirk (personal) (work)

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