BPAI affirms obviousness based on generic motivation "need for higher performance disk caching methods"

Takeaway: In Ex parte Rau, the Board cited with approval a generic motivation to combine based on a statement in the Background of the secondary reference: "there is a continuing need in the art for new disk caching methods and structures, offering lower overhead and higher performance than is presently possible with known methods and systems." Neither the Examiner nor the Board showed any connection between the higher performance and the particular claimed feature relied on by the examiner. Yet if the claimed feature didn't produce the higher performance – if instead, higher performance was caused by something else – then where is the motivation to combine?

Ex parte Rau
Appeal 2009008251; Serial No. 11/021,707; Tech. Center 2100
Decided June 16, 2011

The technology on appeal related to caching in a computer. A representative claim on appeal read:

     1. A method of updating a data cache having a plurality of rows, the method comprising:
     maintaining a list of the rows, the list including a plurality of entries, each entry corresponding to a row and having a key uniquely identifying the row, and further having a count indicating an age of the row;
     sorting the entries by their key;
     searching the list for an entry having a key to a row to be updated if found or added if not found;
     if the entry having the key to the row to be updated is found:
               removing the entry from the list;
               sorting the remaining entries by their count, so that the entry at the beginning of the list is for the oldest row, and the entry at the end of the list is for the newest row;
               appending a new entry at the end of the list that replaces the removed entry, the new entry having the same key as the removed entry, and a count indicating the corresponding row is the newest; and
              updating the corresponding row in the data cache. 

The Examiner rejected the independent claim as obvious over a combination of two references. According to the Examiner, the primary reference taught all limitations except for the sorting by count and appending at the end of the list. The Examiner relied on a secondary reference for these limitations. As a reason for combining the references, the Examiner offered an explicit motivation in the secondary reference: "there is a continuing need in the art for new disk caching methods and structures, offering lower overhead and higher performance than is presently possible with known methods and systems."

In the Appeal Brief, the Applicant made several arguments: the primary reference did not teach removing the entry when found; no expectation of success in the combination; and teaching away. The Applicant did not contest the motivation to combine.

On appeal, the Board considered each of the Applicant's arguments, and found no error in the Examiner's positions. The Board therefore affirmed the obviousness rejection.

Finally, the Board noted with approval the Examiner's explicit motivation to combine, taken from the secondary reference:

We also agree with the Examiner’s explicit motivation that combining the references would be obvious since “there is a continuing need in the art for new disk caching methods and structures, offering lower overhead and higher performance” (Ans. 6). The Supreme Court has stated that “[t]he combination of familiar elements according to known methods is likely to be obvious when it does no more than yield predictable results.” KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 419 (2007). 

My two cents: I don't have an opinion on the overall conclusion of obviousness. But I think the Board was completely offbase in using this generic motivation to combine as a grounds for affirmation.

I've seen plenty of cases in which generic motivations – stronger, faster, cheaper – were convincing. Take, for example, an obviousness rejection based on modifying the primary reference to use titanium instead of steel because the secondary reference teaches that titanium is lighter. Sounds pretty convincing because the generic benefit – reduced weight – is directly tied to the modification.

That's not the case here, not by a long shot. First of all, the motivation relied on was in the Background of the reference:

In view of these and other deficiencies associated with prior art methods of implementing a disk cache and replacement strategy, a continuing need exists in the art for new disk caching methods and structures, offering lower overhead and higher performance than is presently possible with known methods and systems.

All the Background section tells me is that a need exists. Strictly speaking, this statement doesn't even tell me that the reference solved the problem. But let's assume a POISTA would interpret this statement as also implying "and we're going to tell you how we solved it".

Even so, this statement doesn't doesn't tell me how the claimed invention in the reference solved the problem. Yet unless the specific teaching relied on in the rejection (here, sorting by count and appending at the end of the list) was the feature that actually produced the benefit (here, higher performance), that teaching can't properly serve as a motivation to combine.

Why should we assume – based on the single statement quoted above – that it was sorting by count and appending at the end of the list that produced higher performance? Maybe sorting by count and appending at the end of the list were already known in the art, and the higher performance was produced by some other feature not relied on by the Examiner. Maybe sorting by count and appending at the end of the list were involved in achieving higher performance, but only in combination with other features.

I'm always suspicious of explicit motivations to combine, because Examiners often take them out of context. References disclose lots of features, and lots of benefits. Don't assume that the cited benefit is actually produced by the feature you're claiming. Read the reference carefully and decide for yourself.