Advanced Ground Information Systems (AGIS), which owns US Pat. Nos. 7,031,728 ("the 728 patent") and 7,672,681 ("the '681 patent"), sued Life360 for patent infringement. In response, Life360 argued that the claim term "symbol generator" invoked MPF claiming under §112, 6th paragraph, and that the specification failed to disclose adequate structure for the "symbol generator," therefore, the asserted claims were indefinite under §112, second paragraph. About the limitation at issue (here, “symbol generator”), although there is no "means" term in the claim, the District Court held that "symbol generator" is a MPF limitation, because the term is simply a description of the function performed. As a result, the District Court applied 112, 6th paragraph, and ruled the claim is invalid as indefinite under 112, 2nd paragraph, because no algorithm, which is corresponding structure, for performing "generating" function is disclosed in the specification.

In reviewing the district court’s decision, the Federal Circuit laid out a two-step inquiry for indefiniteness. The first step is to determine whether the relevant claim terms are MPF limitations. If the terms are MPF limitations, the second inquiry is “whether the disputed claim terms have "corresponding structure, material or acts described in the specification to which the term will be limited.” The Federal Circuit affirmed District Court’s decision that the claims are indefinite, and concluded that the asserted claims are invalid. The reasoning is that "symbol generator" does not describe any structure, and thus is to subject to §112, 6th paragraph; and the specification does not disclose an algorithm for performing the claimed function. In doing so, the Federal Circuit found AGIS's arguments, based on expert testimony that "symbol generator" connotes structure to a person of ordinary skill in the art, unpersuasive.

The Federal Circuit found the expert testified that "symbol generator" is a term coined for the purpose of the patents-in-suit, and that terms "symbol" and "generator" are known within the field of computer science. In this regard, the Federal Circuit indicated that irrespective of whether terms "symbol" and "generator" are terms of art in computer science, the combination of terms as used in the context of the relevant claim language suggests that it is simply description of the function being performed, that is the generation of symbols.

Finally, the Federal Circuit held that the MPF limitation at issue is indefinite, because specifications do not disclose an operative algorithm for the claim elements reciting "symbol generator.” The Federal Circuit indicated, citing Net MoneyIN, Inc. v. VeriSign, Inc., that “in a case of computer-implemented functions, we require the specification disclose an algorithm for performing the claimed function.”