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How to read patents

(See also: State of the art - what can prove prior art)

When reading patents, the most important part of a patent are the "claims". These are the ideas that are covered by the patent. It's a common mistake think of the abstract as a summary - it is not a summary. Prior art can be useful for invalidating all or part of a patent if it shows that someone has already done what's in the claims.

Focus on the claims, not the abstract!

The claims are not always easy to find. Look for a numbered list, introduced usually by either:

  • What we claim is
  • What is claimed is

Independent and dependent claims

There might be ten or a hundred claims. Most of these will be "dependent" claims which claim something in addition to a previous claim. For example:

  1. A box that makes noises.
  2. A box as claimed in claim 1, wherein said noises resemble a monster.
  3. A box as claimed in claim 2, wherein said monster noises are scary.
  4. A box as claimed in claim 1, wherein a toy monster sits.

Here, claims 2, 3, and 4 are dependent claims. Claim #1 is an "independent" claim. This is important because if the independent claims don't cover software ideas, then the dependent claims usually don't cover software ideas. So, to determine if a patent is a software patent or not, you usually only have to read the independent claims.

Can you help? We need references to confirm (or correct) this explanation.


Example: US6,125,447

Take US patent 6,125,447. Like all patents, it has a name, an abstract, and claims. The claims are what you need to find prior art for.

  • The name is "Protection domains to provide security in a computer system". There are many ways to implement such a system. The only way to check for an infringement or for prior art is by reading what specific implementation is described in the patent - you'll find that in the claims.
  • The abstract (also not too important) is:

A method and apparatus are provided for maintaining and enforcing security rules using protection domains. As new code arrives at a computer, a determination is assigned to a protection domain based on the source from which the code is received. The protection domain establishes the permissions that apply to the code. In embodiments where the code to be executed by the computer belongs to object classes, an association is established between the protection domains and the classes of objects. When an object requests an action, a determination is made as to whether the action is permitted based on the class to which the object belongs and the association between classes and protection domains.

  • And here's the claims, the only really important part. There are twenty-four claims, but we'll only print the first eight claims here. You can see that claims 1 and 7 are independent claims (important), and the rest are dependent claims (usually much less important).

What is claimed is:

1. A method for providing security, the method comprising the steps of:

establishing one or more protection domains, wherein a protection domain is associated with zero or more permissions;

establishing an association between said one or more protection domains and one or more classes of one or more objects; and

determining whether an action requested by a particular object is permitted based on said association between said one or more protection domains and said one or more classes.

2. The method of claim 1, wherein:

at least one protection domain of said one or more protection domains is associated with a code identifier;

at least one class of said one or more classes is associated with said code identifier; and

the step of establishing an association between said one or more protection domains and said one or more classes of one or more objects further includes the step of associating said one or more protection domains and said one or more classes based on said code identifier.

3. The method of claim 2, wherein said code identifier indicates a source of code used to define each class of said one or more classes.

4. The method of claim 2, wherein said code identifier indicates a key associated with each class of said one or more classes.

5. The method of claim 2, wherein said code identifier indicates a source of code used to define each class of said one or more classes and indicates a key associated with each class of said one or more classes.

6. The method of claim 2, wherein the step of associating said one or more protection domains and said one or more classes based on said code identifier further includes associating said one or more protection domains and said one or more classes based on data persistently stored, wherein said data associates code identifiers with a set of one or more permissions.

7. A method of providing security, the method comprising the steps of:

establishing one or more protection domains, wherein a protection domain is associated with zero or more permissions;

establishing an association between said one or more protection domains and one or more sources of code; and

in response to executing code making a request to perform an action, determining whether said request is permitted based on a source of said code making said request and said association between said one or more protection domains and said one or more sources of code.

8. The method of claim 7, wherein the step of establishing an association between said one or more protection domains and said one or more sources of code further includes establishing an association between said one or more protection domains and said one or more sources of code and one or more keys associated with said one or more sources of code.

How to spot "software" claims

Patents can include claims on a mix of software and hardware ideas. When we say "hardware ideas", we mean claims that can only by infringed by making or distributing hardware. Here are example(s) of keywords that indicate that a claim might cover an idea which a software developer or software distributor might use:

  • A method for... (at least in the USA)

Some patents are partly hardware, partly software

Remember that patents can be partly hardware, partly software. For example, a patent could list various claims about a mechanical process and then add a later claim along the lines of "The method described in Claim #1, performed by software on a computer".

Files are not just bits

To be a good technician / computer scientist, you have to be able to see past the purpose of files. A video is no more special than an image or a song. They're all just files of bits. But, in law, the purpose is important.

Related pages on ESP Wiki

External links

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