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#title: LZW compression: conjugations patented

#descr: The LZW data reduction method is moderately ingenuous and moderately
efficient.  It was patented as US 4558302 and, against the letter and
spirit of the written law, as EP 129439.   Better solutions are
meanwhile available, some non-patented.  But due to the inertia of
de-facto standards such as GIF, ZIP, PDF etc, the LZW patent it is
still causing a lot of grief.  It is as if the conjugations of the
English language had been patented.

#TeW: The authors of a popular PDF viewer explain how the Unisys LZW patents
are causing them trouble

#Uya: Unisys study warns EU against Swpat

#aoa: a report written by Unisys for the European Commission's General
Directorate Enterprise on pooling Open Source Software for
administration.  This report warns and explains in detail that
software patents as a serious threat for open source software and the
IT sector at large.

#DiP: The license conditions of the patentee

#Ude: Detailed Documentation

#Gni: GIF support may not be included in free libraries.  A developper
reports about his difficulties with Unisys.

#Eop: EPO patent descriptions cannot be viewed, printed or manipulated under
free Unix systems, because they contain LZW compression.  The Acrobat
Reader provides only a very incomplete and non-free replacement.  It
is tedious to view EPO patent descriptions with Acrobat, because they
are organised as one PDF document per page.  Concatenating pages can
normally be done using %(e:imagemagick), but this program too can not
handle the LZW compression because of patent problems.

#Wba: What about patents?

#gpW: gzip was developed as a replacement for compress because of the UNISYS
and IBM patents covering the LZW algorithm used by compress.

#IWd: I have probably spent more time studying data compression patents than
actually implementing data compression algorithms. I maintain a list
of several hundred patents on lossless data compression algorithms,
and I made sure that gzip isn't covered by any of them. In particular,
the --fast option of gzip is not as fast it could, precisely to avoid
a patented technique.

#TyW: The first version of the compression algorithm used by gzip appeared
in zip 0.9, publicly released on July 11th 1991. So any patent granted
after July 11th 1992 cannot threaten gzip because of the prior art,
and I have checked all patents granted before this date.

#Dlo: During my search, I found two interesting patents on a process which
is mathematically impossible: compression of random data. This is
somewhat equivalent to patents on perpetual motion machines. Check
here for a short analysis of these two patents.

#yds: Unisys responds to Questions

#oio: In April 1999, I asked the following two questions to Unisys: when
does your patent on the LZW compression algorithm expire?  do you
agree that an algorithm is equivalent to a theorem, in the sense that
for example, the Pythagorean theorem can be considered as an algorithm
to find the length of the hypotenuse of a right triangle?

#cna: They answered this to the first question:  The basic U.S. patent
expires in June, 2003. Variants on the basic LZW patent run for about
20 years and further U.S. applications are pending.  However, their
answer to the second question was less precise: We do not agree or
disagree with your statement regarding the relationship between an
algorithm and a theorem.

#Wje: I hope that everyone here is going to celebrate on June 20, 2003.
That's when US patent 4,558,302 expires. That is the patent that
unisys has on the lzw compression algorithm that is used in GIFs.

#mnK: Informatiker an Uni Tübingen über LZW

#aga: Aufürhliche Informationen über das LZW-Patent, seine Verwertung durch
UniSys sowie das IBM-Patent 4814746 auf das gleiche Verfahren.

#vmr: Explanation of the LZW Algorithm

#nro: Patents on Compression Algorithms

#iiW: Unisys License Info

#iLs: Unisys Licensees

#MoG: RMS on GIF

#tWF: Lecture in German on the GIF format

#OWs: One company CEO wrote to us about his troubles with the Unisys patent
licensing conditions:

#WsW: I make a product called X which is a Y web server extension for
dynamic image manipulation. I'd like to include GIF support in the
product but its difficult to know how to do this effectively. The
Unisys licensing restrictions are so severe that I wouldn't be able to
offer a free trial version. Also I don't even see that I'm really
responsible since I'm just providing a tool to enable others to put a
solution together. It's a standard story.

#Aae: An software entrepreneur working mainly in the field of individual
solutions remarkes:

#DWK: Due to the LZW patent, the development of user interfaces that run
within a web browser has come to a halt.  When you want to run complex
ASP solutions in a browser, you can in many fields of application not
avoid dynamic generation of graphics.  The problem of picture formats
currently creates a situation where no more software is developped in
this area although many beautiful solutions would be conceivable.

#Dxe: This trouble is hitting us as well.  We are stuck with the fruits of a
development which we can no longer exploit without legal dangers.

#AWw: A CEO of an SME in the embedded software field writes:

#Dhh: Die Anbieter der von dem LZW-Patent und ähnlichen Patenten bedrohten
Software müssen stark reagieren, denn ihre Kunden fühlen die
eingesetzte Software bedroht. Überall wo sich solche Unsicherheit
breit macht, ziehen die Kunden es vor, Systeme einzusetzen, von denen
sie vermuten, daß Sicherheit hinsichtlich der Lizenzen besteht. Mit
der Zeit wird sich zeigen, daß bei keiner Software Sicherheit
bezüglich der Lizenzen besteht (siehe die aktuelle JPEG-Diskussion).
Deshalb werden sich die Kunden zu Anbietern hin orientieren, die von
der Größe des Patentportfolios den Eindruck einer gewissen Sicherheit
(Abschreckungs-Potential) bieten.

#Del: Daraus erklären sich allerlei bekannte Reaktionsmuster in der Branche,
die einzeln oder in Kombination auftreten können:

#Wrn: Wer kein entsprechendes Patentportfolio hat

#keS: kämpft gegen den Unsinn der Software-Patente

#Kue: übt Kritik nicht laut, um keine schlafenden Hunde zu wecken

#sre: sucht die Nähe (Geschäftsbeziehungen) zu Inhabern eines
Patent-Portfolios, weil er sich damit deren Schutz erhofft (in der
deutschen Automatisierungstechnik dürfte Siemens der Wunschpartner
sein)

#gze: glaubt daß er schon irgendwie zu einem Patent-Portfolio kommen wird
(Glaube versetzt Berge)

#bPr: baut ein Patent-Portfolio auf

#Wet: Wer ein entsprechendes Patentportfolio hat

#vWe: versucht das friedlich zu begründen (%(q:beweist Innovationskraft))

#vWf: versucht das als Abschreckungswaffe zu begründen

#dmr: droht schon mal ganz allgemein, um Kritiker ruhigzustellen und/oder
neue Geschäftspartner zu finden

#kWf: kämpft für den Unsinn der Software-Patente

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