Fighting Bad Patents with Good Prior Art

This week the Open Invention Network, of which Red Hat is a founding member, opened a new chapter with its Linux Defenders project to address patent threats against open source. Yesterday, OIN posted three of the patents that Microsoft asserted in a recent lawsuit against TomTom. OIN is inviting interested persons to contribute prior art to help invalidate those patents.

We heartily support this effort. To advance it, we thought it might be helpful to give some background on the problem of bad patents and how the FOSS community can help address them.

While examiners at the U.S. Patent and Trademark Office have a duty to grant patents only on inventive technologies (and not on known technologies ), they often have trouble finding references demonstrating that the subject matter of a patent application is already known. This is particularly true in the software field. PTO examiners have limited resources and incomplete access to the best prior art. The result is that examiners grant software patent applications that would be rejected if a better prior-art search were done.

In patent lingo, “prior art” refers to evidence of what was already known in the field. There’s no limit on the form the prior art may take, so long as it was publicly available prior to the invention date. It could be an earlier patent, but it could also be lots of other things, including software code, journal articles, white papers, textbooks, instruction manuals, and slides handed out at technical conferences. It could even be a software application that you wrote and posted on a bulletin board years ago. Using prior art, a patent challenger, in litigation or through a proceeding in the PTO called a reexamination, can invalidate a patent on the basis that it was not truly inventive.

To determine the relevance of prior art to a particular patent, however, it’s important to understand what the patent actually protects. Newcomers to the world of patents sometimes do not realize that the patent only protects the inventions defined by the language in the “claims.” Patents contain a lot of language other than claims, such as descriptions of how to make and use the patented invention and various embodiments of the invention. Claims are the numbered paragraphs located at the end of the patent, typically preceded by introductory language such as, “What is claimed is:.”

For a successful patent challenge, one must establish that the prior art contains all of the recitations in the claim. But a single prior-art reference need not contain exactly the claimed invention. Validity challenges often combine two or more prior-art references that together render the claimed invention obvious. It’s helpful for a challenger to collect a variety of prior art, because even though the individual pieces in isolation may be inadequate, the collection may establish invalidity.

Another sometimes confusing issue is the relevant priority date for prior art. To help establish invalidity, prior art must be shown to pre-date the invention date for the claimed invention. Plainly, the invention date cannot be any later than the filing date for the application that led to the patent, and the law presumes that a patent’s invention date is its filing date.

Confusion arises because the law permits a patent holder to establish an invention date that is up to year earlier than the filing date, thereby potentially defeating prior art from after the invention date but before the filing date. For example, if the filing date is April 29, 2009, the patent holder is allowed to establish actual invention as far back as April 29, 2008. For this reason, the most useful prior art is art dated more than year before the filing date for a patent, but prior art dated anywhere in the year before the patent’s filing date is still helpful. The prior-art dates relevant to the Microsoft patents are set forth in their posting on the Linux Defenders site.

There is a lot more to be said about prior-art searching, but this is a start. Because patent issues are important and the potential for community action against bad patents is so great, Red Hat will continue the discussion on patents and prior art at the Red Hat Summit and JBoss World in Chicago this coming September 1-4. Hope to see you there.