Patent drafting often seems to require the impossible. The applicant must describe the invention broadly (and narrowly, but without letting the narrow description limit the broad one), provide technical advantages (but without limiting the invention to those advantages), transform detailed embodiments into abstracted concepts, avoid any possible inconsistency (lest the inconsistency be used against the applicant), and so on.  One wrong word can be seized by the accused infringer or patent examiner to create a fatal flaw. Similarly, even when one carefully selects words that match a desired scope, the Patent Office can blow up the meaning under the broadest reasonable interpretation (BRI) standard. And further, the applicant must be absolutely consistent throughout many years of prosecution and later inter partes proceeding or litigation.

A recent example is the IPR appeal D'Agostino v. Mastercard International Inc. The patent involvedmethod claims for generating specific transaction codes to be given to a merchant by a customer with increased security. A key aspect of one of the method claims was that the process was limited to a "single merchant" that is initially unidentified.  Specifically, the method includes "receiving a request from said account holder for a transaction code to make a purchase within a payment category that at least limits transactions to a single merchant ... prior to any particular merchant being identified as said single merchant."  Then, after several further steps, the method concludes with authorizing payment for the purchase.  

The applicant not only had clear disclosure in the specification, but was consistent in the extended prosecution and defense of the patent, that the single merchant limitation truly did mean what it says.  The PTAB had relied on an interpretation in which the single merchant limitation could be satisfied by a chain of stores. The Federal Circuit disagreed and found such an interpretation unreasonable. The Federal Circuit specifically reviewed the specification and prosecution history to confirm that the applicant had not made any statements that would justify the unreasonably broad interpretation:

In this way, the Federal Circuit found that the prosecution history and specification reinforced the evident meaning of the claim language, irrespective of whether there was any disavowal. The claim language could not be read so broad as to include both a pre-identified chain of stores and a later selected specific store in the chain. The Federal Circuit used the Board's reasoning to point out that if the merchant is the Target chain of stores, then the claims exclude that scenario because that example does not limit the transaction to that single chain, but rather a single store in the chain.

The case illustrates how difficult it can be to overcome PTO interpretations under the BRI. While the applicant was ultimately successful, it required the decision maker to consistently apply logic and analysis across multiple elements of the claim. Further, it required the applicant to have been completely consistent over many years and multiple battles. In any event, one way to attack unreasonable interpretations is to point out how such interpretations are inconsistent with explicit claim language.