Examiners often dislike negative claim limitations. Adding a negative limitation without strict support in the specification can therefore be difficult. But if properly supported, there is nothing inherently wrong with a negative claim limitations.
Sometimes it can be difficult to convince an Examiner that a prior art references fails to show a certain negative claim element. In a recent PTAB case related to networking and broadcasting of available bandwidth, the Applicant claimed certain actions that were taken "whether or not" a bandwidth threshold was reached. The examiner relied on a single prior art reference that performed the claimed broadcasting when reaching a bandwidth threshold. To address the "whether or not" element, the Examiner then cited to prior art disclosed in the background of the cited reference that used a time-based broadcast (and thus allegedly performed the broadcasting whether or not the claimed bandwidth threshold was reached). Claim 1 is set forth below:
The PTAB correctly rejected this approach. For anticipation, the PTAB confirmed that the claimed subject matter must be met by the disclosure of a single embodiment in the disclosure, not by a combination of different embodiments, and must be arranged in the same way as recited in the claims. Thus, combining the background approach with the approach of the invention was improper.
As noted above, Examiners can be sticklers for support when adding negative limitations. Here, the key "whether or not" limitations was added during prosecution. The applicant cited to the specification for support, which noted near the end that the information will be sent periodically, "whether or not the available bandwidth ... has changed by any particular amount." While this supported the general idea as claimed, it is interesting that there was no express mention of thresholds.
The application, 12/653,264, was prepared and prosecuted by Ron Slusky, who writes a great book on how to use the problem-solution approach for claim drafting. This appeal showcases that approach and how it enables the applicant to present good arguments for differentiating cited art that fails to recognize the inventive concept being claimed.