Wasn't it Peter J. Holzer who wrote:

>>"Mark Wagner" <mar### [at] gtenet> wrote in message
>>news:394313ef@news.povray.org...
>>>
>>> Mark Gordon wrote in message <39421BB5.AB8BA839@mailbag.com>...
>>> >1984 - LZW compression invented and written up in IEEE Computer
>>> >1985 - LZW patent approved
>>
>>What I do not understand:
>>
>>When LZW was published 1984,
>>how can it be patented in 1985?
>>
>>I mean as soon as I publish an idea in a newspaper,
>>it's not any more possible to patent it,
>>because the idea is general knowledge because
>>was published before
>
>That's not quite correct. The "prior art" rule prevents people from
>patenting things which they did not invent themselves (otherwise
>somebody might patent the wheel and then sue all the car manufacturers).
>If you invent something, you can certainly show it or describe it to any
>number of people and still patent it. However, it might be somewhat
>difficult to prove that you are the inventor, if you show it to too many
>people. As other people already pointed out, it takes some time to
>approve a patent (if fact, 1 year seems to be remarkably short!).

I don't think that "prior art" is the rule in question here. If you
publish details of your invention and then later apply for a patent,
that patent is not going to retrospectively protect you from people
using what you have already published. 

>However, I don't understand something else: When the issue first came up
>in 1993, everybody seemed to think that only the compression algorithm
>was covered by the patent, not the decompression (That's why gzip can
>read .Z-files, but cannot create them). However, the patent cited here
>very clearly mentions decompression, too. Are there two patents about
>LZW?

The owners of the patent wanted people to freely implement decompression
routines. The basic idea being that this would generate a huge user base
of people who had software that could read the files, but anyone who
wanted to create files to distribute to those users would use software
which was licensed to use the compression algorithm.

-- 
Mike Williams
Gentleman of Leisure

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