## Facts

- The patent at issue described a network-based “distributed learning” system implementing a virtual classroom using standard computers connected over a network.
- The system included a presenter computer, audience computers, and a distributed learning server.
- Claim 8 recited a “distributed learning control module” configured to (1) receive communications, (2) relay communications, and (3) coordinate operation of a streaming data module.
- The patent owner alleged several online collaboration products infringed claim 8 and other claims.
- The district court held the “distributed learning control module” limitation was governed by 35 U.S.C. § 112 ¶ 6 (now § 112(f)) and that the specification failed to disclose corresponding structure (an algorithm), rendering claim 8 and its dependents indefinite and invalid.
- The case reached the Federal Circuit; rehearing en banc was granted on the limited question of when § 112(f) applies to computer-implemented limitations that do not use the word “means.”

## Issues

1. Whether a claim term lacking the word “means” may still invoke § 112(f), and what standard governs overcoming the presumption against § 112(f).
2. Whether “distributed learning control module” is a § 112(f) means-plus-function limitation and, if so, whether the specification discloses sufficient corresponding structure (an algorithm) to satisfy definiteness.
3. Whether the district court improperly narrowed certain “graphical display” claim terms by importing limitations from embodiments, thereby affecting non-infringement determinations on other claims.

## Decision

- The Federal Circuit (en banc in relevant part) rejected the prior “strong” presumption against applying § 112(f) when “means” is absent, substituting an ordinary presumption that can be rebutted by showing the term fails to recite sufficiently definite structure.
- The court held “distributed learning control module” invoked § 112(f) because “module” functioned as a generic placeholder and the limitation was drafted in a traditional function-reciting format without sufficient structural meaning.
- The court affirmed invalidity of claim 8 and its dependent claims as indefinite because the specification did not disclose an algorithm corresponding to the claimed computer-implemented functions.
- The court vacated the non-infringement judgment as to certain other claims that depended on overly narrow constructions of “graphical display” limitations and remanded for further proceedings.

## Legal Principles

- The absence of the word “means” creates a rebuttable presumption that § 112(f) does not apply, but the presumption is overcome when the challenger shows the term fails to recite sufficiently definite structure or recites function without sufficient structure to perform it.
- Generic “nonce” terms such as “module” may invoke § 112(f) when used as a substitute for “means” and coupled with function-only claiming.
- For computer-implemented § 112(f) limitations, the required corresponding structure is an algorithm disclosed in the specification; high-level functional description is insufficient.
- If a § 112(f) limitation lacks disclosed corresponding structure for the recited function, the claim is indefinite under § 112 ¶ 2 (now § 112(b)) and invalid.
- Claim construction may not import limitations from preferred embodiments into the claims absent a clear claim or specification basis requiring that narrowing.

## Conclusion

The Federal Circuit recalibrated the presumption governing § 112(f) for limitations that omit “means,” held a “control module” limitation was means-plus-function and indefinite for failure to disclose an algorithm, and remanded portions of the case affected by improperly narrowed constructions of other claim terms.


Williamson v. Citrix Online, LLC, 792 F.3d 1339 (Fed. Cir. 2015)