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GIF Tax/LZW Patent
From: David Farber <farber () central cis upenn edu>
Date: Tue, 3 Jan 1995 14:00:29 -0500
As a side issue, while at Bell Labs I implemented one of the first (maybe the first) run length compression schemes that I called Crunch. That was in 1959-60. I suspect it may be relevent to this also Dave Date: Tue, 3 Jan 95 14:00:05 -0500 From: shap () viper cis upenn edu (Jonathan Shapiro) I'm not expert on patent law OR compression, but I've had occasion to read up on the LZW patents at a very high level. The LZW patent family is contested by a number of parties who claim to have independently invented the basic technologies involved. If any of you are interested enough to want to read a synopsis, check out the FAQ in comp.compression. Among other things, it will point you to a collection of implementations of the various algorithms in the LZW family. Among the files you will find a readme that lists all of the patents that were known to the collector, along with a human-readable description of what they cover. There are many conflicts among these patents. An interesting issue is who has liability. Compuserve offered a royalty free license for this technology for many years. Implicit in the concept of a license is that the licensor owns the subject matter of the license. If I implemented and used the technology under that license, and the license was invalid, then Compuserve has exposed me to liability, and may be responsible for that exposure. In order to apply, the relevant patent must predate 1987 (the initial release of the GIF standard), so a case could be made that Compuserve misrepresented their ownership of the technology in the first place. If you are a provider of a GIF implementation, and Unisys has come after you for infringement of the LZW patent, you may be able to sue Compuserve for the damages. Many of the LZW patents are written in such a way as to cover ENcoding, but not DEcoding. Depending on which patents Unisys has obtained, your product may not infringe unless it *generates* GIF files. Another possibility to consider is that Unisys has not managed to tie down all of the LZW patents. It might be possible to form a temporary alliance around one of the earlier patents in order to countersue Unisys and possibly get their patent thrown out. It seems a safe prediction that Compuserve will ultimately release some new standard, say GIF95, based on the compression algorithm used in GNU ZIP, which is not currently encumbered by patent. It would certainly be simple enough to convert the existing images. Some food for thought: Though the media have covered primarily compression and encryption patents, this sort of problem is occuring in more and more parts of the software industry. Perhaps software patents are not such a great idea? One wonders if something like a class action suit could be brought against the patent agency on the grounds that by refusing to use software professionals to assess new patent applications, they knowingly and willfully conspired to restrain trade, and that many of the patents they granted fell outside of what was patentable under the law. If this could be done, perhaps the older patents could be eliminated. The most obvious thing to do about the GIF standard is to start using JFIF (JPEG), which is a better technology in any case. Unfortunately, the JFIF standard specifies an encoding that appears to be patent encumbered... Jonathan
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- GIF Tax/LZW Patent David Farber (Jan 03)