Claim differentiation applies on a limitation-by-limitation basis and is not vitiated by the inclusion of additional limitations in the differentiating claim. Here, for example, a dependent claim specifying that a “web browser process” is capable of “direct” access to the Internet was found to imply that no such requirement was present for the “web browser process” in the corresponding independent claim even though the dependent claim contained additional limitations that would themselves distinguish the dependent claim as a whole from the independent claim. “While [the accused infringer] is correct that [the dependent claim] adds another limitation compared to [the independent claim], that argument does not change the fact that the [relevant] limitation would be rendered superfluous.” It may therefore be acceptable to group limitations added for claim differentiation in one or a small set of dependent claims rather than requiring that they be claimed separately.
Background / Facts: The patent being asserted here is directed to a way of protecting a computer from malware. The independent claims recite downloading untrusted content from the Internet via a first “web browser process” and executing it in a second “web browser process” where it cannot damage important files. Dependent claims further specify that the claimed “web browser process” is capable of directly exchanging data with the Internet—i.e., without having to use another web browser process, as a word processor would have to do, for example.
Issue(s): Whether claim differentiation precludes the claimed “web browser process” element in the independent claims from being interpreted as inherently requiring “direct” access to the Internet.
Holding(s): Yes. “If claim 21 already required a capability for ‘direct’ access to the network, then the language of claim 24, which recites that the ‘second web browser process is capable of directly exchanging data with the network interface,’ would be entirely duplicative. Thus, the language of the claims indicates that only in claim 24 does the second web browser have to have a ‘direct’ access capability. While [the accused infringer] is correct that claim 24 adds another limitation compared to claim 21, that argument does not change the fact that the ‘directly exchanges data with a network’ limitation would be rendered superfluous. … Thus, we find [the patentee’s] claim differentiation argument compelling and find that the addition of the direct access capability limitation in claim 24 gives rise to a presumption that claim 21 lacks such a limitation.”