The Claims Interpreted Report

Another Example of Claim Differentiation

By Chris Francis

Categories: The Claims Interpreted Report

Claim differentiation was one factor that led the Federal Circuit to affirm the PTAB’s claim construction in the appealed IPR in Realtime Data, LLC v. Iancu (Fed. Cir., Appeal No. 2018-1154, decided Jan. 10, 2018).  This case also involves an interesting issue regarding obviousness and motivation to combine, and Dennis Crouch has summarized that issue on his blog at  This quick post below focuses on the claim construction of the phrase “maintaining a dictionary.”

By way of background, the opinion notes that “dictionary encoding is a form of lossless data compression that assigns a code word to a particular data string, maps that code word to an index, and replaces every matching data string with the corresponding code word…This assignment would be mapped to an index, or dictionary.”

The independent claim at issue reads:

1. A method for compressing input data comprising a plurality of data blocks, the method comprising the steps of:

detecting if the input data comprises a run-length sequence of data blocks;

outputting an encoded run-length sequence, if a run-length sequence of data

blocks is detected;

maintaining a dictionarycomprising a plurality of code words, wherein each code

word in the dictionary is associated with a unique data block string;

building a data block string from at least one data block in the input data that is

not part of a run-length sequence;

searching for a code word in the dictionary having a unique data block string associated therewith that matches the built data block string; and

outputting the code word representing the built data block string.


In the IPR, the patent owner admitted that the prior art discloses dictionary encoding, but argued that the prior art did not disclose “maintaining a dictionary” because the prior art generates a new dictionary for each data segment while the challenged patent processes an input data stream through a single dictionary (and that single dictionary only resets to its initial state when full).  The Board did not construe “maintaining a dictionary” because dependent claim 4 further defined this phrase and the Board found that the prior art disclosed all elements of dependent claim 4.

The Federal Circuit affirmed the Board because, among other reasons, the specification described the patent owner’s proposed claim construction as a possible embodiment and does not imply that it is a mandatory part of “maintaining a dictionary.”  Further, the Court states that dependent claim 5 actually claims the further definition of “maintaining a dictionary” that the patent owner uses in the claim construction of that term.  “The fact that claim 5 ‘further’ adds this step indicates that this step was neither a necessary element of dependent claim 4 nor required in the step of ‘maintaining a dictionary’ in claim 1.”  In other words, claim 5 provides differentiation that prevents the interpretation proposed by the patent owner.   Notably, claim 5 was not at issue in the IPR that is being appealed in this case. 

If nothing else, this case is a reminder that claim differentiation is alive and well and should be considered and used to your advantage in drafting claims and the specification.