Patent claims drafted by patent attorneys can sometimes be difficult to read, but there is good reason. Every word put in (or left out of) a patent claim can have a significant legal impact. A recent US court decision highlights just how important it is to get the wording right.

A particular patent claim in Silicon Graphics, Inc. (SGI) v. ATI Techologies, Inc Nos. 08-1334, -1353 (Fed. Cir. June 4, 2010) defined a computer system having a component utilising "a rasterization process which operates on a floating point format" ('floating point' is a particular way of representing numbers in a computer). The infringement decision in this case turned on the interpretation of the word 'a'.

The ATI product accused of infringing the patent did have a component which performed a "rasterization process." However, the rasterization process in the ATI product used both 'floating point' numbers and 'fixed point' numbers (a different number format which was not mentioned in the patent claim). The question for the court was whether this product still infringed the wording of the patent claim, by using both number formats.

At first instance, the District Court held that the ATI product did not operate in a floating point format "as a whole", and so found that the patent was not infringed.

However, on appeal, the Federal Circuit overturned this decision, stating:

"The use of the indefinite article "a" in the claim, when coupled with the list of processes provided in the specification, makes it clear that the claims' references to "a rasterization process" means "one or more rasterization processes."

The limitation "a rasterization process which operates on a floating point format" therefore means that "one or more of the rasterization processes (e.g., scan conversion, color, texture, fog, shading) operate on a floating point format.... Nowhere does the specification teach that all rasterization processes must operate on a floating point format."

Accordingly, it was held that as long as there was one rasterization process using 'floating point' numbers (even if different number formats were also used), the claim would be infringed.

This case highlights the importance of engaging with your attorney to get the claim wording right, and ensure your product is properly protected.

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