Speaker Andrew Tridgell
Time 2010-01-22 10:30
Conference LCA2010

I am not a layer, that is not the point of this talk. The first part of this talk is a tutorial for an engineer on how to interact with patent lawyers. The second part is to lower your exposure to patent attacks.

Patent lawyers are shy creatures, e.g. platypus.

Patent defence starts of with the egineers. The patent attorneys are there to guide and validate. They probably don’t know your code. You are the one who understands you code and will have to explain if you code matches or does not match some patent out there.

Need to learn to read patents. Not just the abstract. Definitely not just the title. Prior art defence is really difficult and hard to pull off. Non-infringement easier to do.

It is dangerous to read patents. If you knowingly infringe a patent you get 3 times the damage. For most FOSS projects, 1 times the damage will kill the project anyway, 3 times the damage will end up in the project still being dead. What is the point of walking around a mine field with a light bulb to protect you? Wouldn’t it be better to walk around the mine field?

Types of defense:

  • non-infringement: “we don’t do that” - the best defense.
  • prior art: “somebody did that before [the patent was filed]” - very tricky. Very common, very unsafe to use as primary means of defense.
  • invalidity: “You can’t claim that” - almost impossible.

Independent vs dependent claims

  • dependent claims - claim refers to earlier claim. This is the same as an earlier claim plus an extra bit.
  • independent claims

Only have to look at independent claims for non-infringement defence.

For prior art defence need to defend against all types of claims.

Example patent

NZ9647631: A large red car

Filed 22nd Jan 2010.

21st Jan 2009, prior art after this date doesn’t count.

Abstract: A transport system of the entertainment of children.

Abstract. Skip it on first reading Go down to what is claimed.

Claim 1: A transport system consisting of

* A red car
* with shiny plastic panels

Independent claim. Attack the claim elements (I don’t do that), not the preemble. And is implied between the elements. If you do have a red car with shiny plastic panels, but is not a transport system, you are attacking the preemble, might be possible, going for the elements is usually better.

If car is green, then patent does not apply. If car has metal panels, patent does not apply.

Claim 2: The system of claim 1, with multi-coloured wheels

Dependent claim. For non-infringement defence, forget.

Claim 3: The system of claim 2, drive by a green dinasour.

Dependent claim. For non-infringement defence, forget.

Real patent

United States Patent

Patent number 5,719,941

Be careful with OCR process, ensure OCR hasn’t got important term wrong. Need to check the PDF file just in case.


Read this, but don’t stop at this point, or you will be doing yourself a disservice.




May leave head spinning so you don’t understand the claims, skip and refer back as required.

What is claimed is:

Doesn’t stand out, hard to find. This is what matters. First claim is likely to be independent claim.

What do the words mean? What is a client?

What do the words mean in the context of the patent?

Need to highlight sequence of words that you don’t do. Patents are usually very specific. Only need to show that you don’t do one specific part. A missing comma could be significant.

Prior Art

Not a panacea. Very hard to kill all claims. Have to knock of every claim. Claims are often interpreted much more specifically than engineers expect. Have to interpret the claims as broadly as possible. This is the opposite of non-infringement defence where you have to interpret the claims as narrowly as possible.

Patent can not get final rejection. A patent can always come back again.

Patent file is a list of all communication between patent and patent office concerning the file. Can include narrowing down of the patent. E.g. patent office says points are not patentable, and client says they misunderstood the meaning of one of the words.

Can say if claims are narrowly defined, then we are non-infringing, otherwise if claims are broadly defined, then there was prior art.

What can we do?

Patents will become more and more a problem for the FOSS community.

We need to be the toughest meanest target for patent attacks.

Build workarounds. Publish workarounds. Patent holder may miss on on royalty from proprietary companies. Patent holder won’t want to attack FOSS projects. If the proprietary companies find a work around they will keep it secret, the FOSS community won’t.

The problem is being able to communicate openly about patents without upsetting the company lawyers because it could be argued that patents were knowingly infringed.