January 7, 2019

The United States Patent Trademark Office (USPTO), issued updated examination guidance (Updated Guidance) for examining software claims defining an invention using functional language on January 7, 2019. The Updated Guidance requires all patent owners and representatives to be especially careful to review claims for generic structures described in functional terms, and when such generic structures are present in claims to ensure the specification provides explicit mention of the generic structures and how they perform the claimed functions.

Overview of Updated Guidance

The Updated Guidance sticks closely to the principles that the Federal Circuit articulated in Williamson v. Citrix Online, LLC, 792 F.3d 1339, 1349 (Fed. Cir. 2015) (en banc). As held in Williamson, there is no longer a presumption that claim limitations lacking the term “means” are not subject to 35 U.S.C. 112(f) . Any substitute term acting as a non-structural generic placeholder for the term “means” will invoke 35 U.S.C. 112(f) (e.g., “mechanism for,” “module for,” “component for,” “unit for,” etc.). Examiners will apply 35 U.S.C. 112(f) if the claim limitation uses the term “means” or any generic placeholder that is modified by functional language, but not modified by sufficient structure for performing the function.

The change in the law imparted by Williamson and echoed in the Updated Guidance not only makes it easier to have claim terms treated under 35 U.S.C. 112(f), but also makes it more likely that claims treated under 35 U.S.C. 112(f) will also be subject to 35 U.S.C. 112(a) and 35 U.S.C. 112(b) issues. If 35 U.S.C.112 (f) is invoked for a computer-implemented claim limitation, the specification must disclose an algorithm for performing the claimed specific computer function. The structure disclosed in the specification must be more than a general purpose computer or microprocessor. The algorithm may be expressed in any understandable terms including a mathematical formula, a flow chart or any other manner that provides sufficient structure. The algorithm must be sufficient to perform the entire claimed function. In other words, if the means-plus-function limitation has more than one specialized function, then the specification must disclose adequate corresponding structure to perform all of the claimed functions.

A computer-implemented claim limitation will be found indefinite under 35 U.S.C. 112(b) if it fails to disclose the computer and algorithm for performing the entire claimed function. It will also lack written description under 35 U.S.C. 112(a) because the specification must disclose the computer and algorithm for achieving the claimed function in sufficient detail that a person of ordinary skill in the art can reasonably conclude that the inventor possessed the claimed subject matter at the time of filing. The specification must explain how the claimed function is achieved to demonstrate that the applicant has possession of it.

A finding of indefiniteness cannot be bypassed by arguing that one of ordinary skill in the art is capable of writing software to convert a general purpose computer to a special purpose computer to perform the claimed function. A person of ordinary skill in the art does not play a role in determining whether an algorithm must be disclosed as a structure for a functional claim element. The inquiry is not whether a person of skill in the art could devise some means to carry out the recited function, but whether the specification itself contains a sufficient precise description of the corresponding structure.

In View of the Updated Guidance, the Following Practical Tips may be Useful:

  • Carefully consider use of generic functional components such as modules, means, etc. that are defined by their functions.
  • When reciting functional components, ensure the functional component is thoroughly described in the specification including an algorithm for performing the claimed function.
  • Consider claiming the invention in alternative ways. If one claim set is to include functional components defined by their functions, consider method claims that do not recite the functional components or a computer-readable medium or system claim that relies on at least one processor to carry out steps defined by computer executable instructions.

Summary and Next Steps

The Updated Guidance does not carry the effect of law, instead instructing Examiners on proper examination procedure. To patent owners and representatives, the Updated Guidance may serve as a possible signal of the USPTO’s intention to provide additional focus on the use of functional language in patent claims and associated descriptions in patent specifications. The Office has requested input from the public within 60 days on the proposed rule changes and on how the Office should implement the changes if adopted. To provide comments, please email the Office at

For questions regarding this information, please contact one of the authors, a member of Polsinelli’s Intellectual Property Department or your Polsinelli attorney. Watch for updates and Polsinelli’s ongoing coverage as these changes develop.

1  35 USC 112(f) ELEMENT IN CLAIM FOR A COMBINATION.—An element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.
2  35 USC 112(f) (pre-AIA 35 USC 112 para 6) or means-plus-function claim language is generally considered to be narrower than terms not treated under 35 USC 112(f). See Lockheed Martin Corp. v Space Systems 324 F.3d 1308 (Fed. Cir. 2003).