Re: BOCU-1 spec

From: Doug Ewell (
Date: Mon Feb 19 2007 - 16:58:59 CST

  • Next message: Philippe Verdy: "RE: BOCU-1 spec"

    Philippe Verdy <verdy underscore p at wanadoo dot fr> wrote:

    >> GIF.
    >> 'Nuff said.
    > What does this "GIF nuff" mean?

    I'm agreeing with you, Philippe. I'm saying that Unisys changed the
    terms of licensing of the LZW algorithm used in GIF, initially waiving
    all licensing fees in the case of freeware (1995) and then removing that
    exception (1999), and that there is nothing preventing IBM from
    similarly changing the terms of licensing of BOCU.

    > Are you talking about the past issue with the GIF format (closed now
    > that patents have expired),

    That particular issue is closed because those particular patents have
    expired. The danger is still present.

    Has anyone else on this list actually read the BOCU patent? Among the
    innovations claimed are:

    a. the method of encoding differences within the range -10FFFF hex to
    +10FFFF hex.
    b. the method of encoding U+0020 as itself to avoid frequent jumps.
    c. the method "wherein the characters requiring higher code point
    numbers are Greek" (i.e. obfuscated).

    This basically covers any method of encoding Unicode code points using
    (a) a difference-encoding method, (b) a strategy to special-case certain
    characters to improve efficiency, or (c) a system that encodes ASCII
    characters using non-ASCII values. This is very far-reaching and could
    be used against all kinds of alternative encoding schemes.

    Read the patent yourself by visiting and searching for
    patent number 6737994.

    > Regarding BOCU and BOCU-1, IBM has correctly revealed to Unicode the
    > patent claims they did, but IBM also provided a valid licence to the
    > ICU project which is placed under the X licence which allows all
    > modifications; so instead of using the specification published by
    > Unicode, it's enough to use the publication made in the ICU project
    > instead, and so the patent issue is immediately closed: you can use
    > both the full BOCU specification and its limited BOCU-1 profile in any
    > project which complies with the X licence requirement (notably, it
    > just requires attribution in the copyright notice, but no further
    > explicit license agreement by IBM, as the license is granted by the
    > free and open-source ICU license).

    You can take that risk if you like. I wouldn't do so without an
    experienced lawyer.

    > If Unicode wants to remove the license agreement, all that it needs
    > then, is to replace the licence grant it got from IBM, by the ICU
    > license and its required attribution notice...

    I'm sure the Unicode Consortium has access to an experienced lawyer, and
    would have done so if it were that simple.

    Doug Ewell  *  Fullerton, California, USA  *  RFC 4645  *  UTN #14

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