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Software Means-Plus-Function Claiming

An element in a patent claim may be expressed as a means or step for performing a specified function. However, 35 USC §112(f) states that a claim limitation expressed in means-plus-function form “shall be construed to cover the corresponding structure ... described in the specification and equivalents thereof.”

Software is often claimed as a sequence of steps, and it is often not clear when software claims invoke the means-plus-function requirements of 35 USC §112(f). Under guidance issued earlier this year, the U.S. Patent and Trademark Office clarified that it will now invoke the means-plus-function requirements of §112(f) when:

  1. The claim limitation recites the term “means” (or “step”) or a generic placeholder (e.g., mechanism, module, device, unit, component, element, member, apparatus, machine, system);
  2. The term is modified by functional language; and
  3. The term is not modified by sufficient structure, material or acts for performing the function.

Once invoked, the specification must describe the “structure” that corresponds to that function. Failure to disclose the structure that performs the claimed function renders the claim invalid for indefiniteness. The structure must be more than a generic computer or microprocessor. Rather, “the corresponding structure ... for a computer-implemented function is the algorithm disclosed in the specification.” Aristocrat Tech. Aus. Pty Ltdv. Int’l Game Tech. 

When drafting a claim, avoid the §112(f) trap by avoiding generic placeholders, e,g. “a software module comprising software instructions.” Also, modify each element with applicable substeps in sufficient detail to accurately describe the algorithm. When litigating, look for the §112(f) issue and whether the specification explicitly describes an algorithm or some way to program a computer/processor to perform the recited function.

Royal W. Craig
410-576-4109 • rcraig@gfrlaw.com