Re: re: @Electron Sheperd
There are for all practical purposes an infinite number of patents.
Here's the rub for a hell of a lot of cases, not just software, and not just using obscure interpretations.
Unless you can afford to hire a specialised team who have intimate knowledge of patent legalese and your own field plus many others, it is nearly impossible to be certain that you are not infringing a patent in some way. There are so many that looking through them yourself will only get you so far. Even such a team could easily miss one.
I have done my own patent research in the past. It turned out my invention was covered by an existing patent, but I was already part way through the application when I stumbled across it. I had done a lot of research beforehand, but the patent in question did not look, at first glance, to be even remotely relevant. It was only when I read in more detail (I was interested in that particular patent outside the purposes of my own patent application) that I found that it mostly covered my own invention. The parts remaining were too trivial to be worth a patent.