The U.S. Court of Appeals for the Federal Circuit overturned a summary judgment of indefiniteness of a claim containing means-plus-function (M+F) clauses covering software, holding that the specification of algorithms performing the claimed function "need only disclose adequate defining structure to render the bounds of the claim understandable to one of ordinary skill in the art." Allvoice Computing PLC v. Nuance Communications, Inc., Case No. 06-1440 (Fed. Cir., Oct. 12, 2007) (Rader, J.).

Allvoice owns a patent that covers an interface between a speech recognition engine and various end-user application programs (e.g., word processing programs). Specifically, when a user speaks into a computer’s microphone, the speech recognition engine converts the speech to recognized words. The recognized words are then processed by the claimed interface to output the recognized words in a format understandable by multiple application programs. In addition, link data associating the original speech to the recognized words is maintained and this link data is updated if, for example, the position of the recognized word is changed using a word processor. The alleged infringer, Nuance Communications, markets voice recognition software under the name Dragon NaturallySpeaking.

The district court, on summary judgment, ruled that certain M+F clauses covering software were indefinite for failure to set forth sufficient algorithmic structure corresponding to the functions recited in the means clauses. Allvoice appealed.

The Federal Circuit reversed, noting that the record did not contain clear and convincing evidence that the computer algorithms disclosed in the specification were insufficient to render the bounds of the claim understandable to the ordinary skilled artisan. To the contrary, the Court found that specification disclosed enough details to constitute an actual algorithm (i.e., the algorithm is the corresponding structure) for carrying out the functions recited in the M+F clauses. The Court noted that the only record evidence regarding this issue was the statement by Allvoice’s expert that the algorithms described in the specification for performing the recited functions could be implemented by one skilled in the art using well-known features of the Windows operating system.

Practice Note: When using M+F clauses to claim a software-based invention, the patent practitioner should ensure that the algorithms described in the specification discloses adequate structure to render the bounds of the claim understandable to one skilled in the art. This is a specific application of the general rule that a M+F clause is definite if a person of ordinary skill in the art would be able to recognize the structure in the specification and associate it with the corresponding function in the claim.

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