The Analogous Art Doctrine Post-KSR: Insights from the Federal Circuit’s Daedalus Decision

by Dennis Crouch

In a short nonprecedential decision, the Federal Circuit affirmed a PTAB IPR decision finding claims 15-25 of U.S. Patent No. 8,671,132 (‘132 patent) unpatentable under 35 U.S.C. § 103 over combinations of prior art references. Daedalus Blue LLC v. Vidal, No. 2023-1313, slip op. at 2 (Fed. Cir. Mar. 13, 2024).  The key issue on appeal was whether the Gelb reference qualified as analogous art for the purposes of the obviousness analysis.  Daedalus unsuccessfully argued that the PTAB erred in two respects: (1) by finding Gelb to be in the same field of endeavor as the ‘132 patent, and (2) by determining that Gelb is reasonably pertinent to the problems addressed by the ‘132 patent.  This post discusses the analogous arts test and provides key guidance to patent attorneys in today’s post-AIA world.

The law of analogous art is a critical concept in determining the obviousness of an invention under 35 U.S.C. § 103. Even if a reference qualifies as prior art under Section 102, it can only be relied upon for an obviousness rejection if it is considered “analogous” to the invention at issue.

To be considered analogous art, a reference must either be (1) from the same field of endeavor as the claimed invention or (2) reasonably pertinent to the particular problem addressed by the inventor, regardless of the field in which that reference was working. In re Bigio, 381 F.3d 1320 (Fed. Cir. 2004). The “field of endeavor” inquiry focuses on the broad scope of the field and not the specific problem being solved. In re Deminski, 796 F.2d 436 (Fed. Cir. 1986). On the other hand, a reference is “reasonably pertinent” if, even though it may be in a different field from that of the inventor’s endeavor, it is one which, because of the matter with which it deals, logically would have commended itself to an inventor’s attention in considering his problem. In re Clay, 966 F.2d 656 (Fed. Cir. 1992). Importantly, a reference need only be either in the same field of endeavor or reasonably pertinent to the problem—it need not satisfy both criteria to qualify as analogous art. Donner Tech., LLC v. Pro Stage Gear, LLC, 979 F.3d 1353 (Fed. Cir. 2020).

While the Federal Circuit has maintained the traditional two-prong test for determining analogous art post-KSR, the court’s decisions suggest a trend towards a more expansive and flexible approach. In Wyers v. Master Lock Co., the Federal Circuit noted that the Supreme Court’s decision in KSR “directed us to construe the scope of analogous art broadly.” 616 F.3d 1231 (Fed. Cir. 2010). Similarly, in Airbus S.A.S. v. Firepass Corp., the Federal Circuit emphasized that the analogous arts inquiry “should take into account any relevant evidence in the record cited by the parties to demonstrate the knowledge and perspective of a person of ordinary skill in the art.” 941 F.3d 1374 (Fed. Cir. 2019).

Patentees also have tools at their disposal to potentially narrow the scope of analogous art. As seen in Netflix, Inc. v. DivX, LLC, explicitly articulating the problem solved by the invention (perhaps within the patent claims themselves) can limit the field of endeavor and pertinent prior art to references addressing that particular problem. 80 F.4th 1352 (Fed. Cir. 2023). Thus, while the overall trend post-KSR may be towards a more flexible analogous arts test, strategic patent drafting can still play a role in circumscribing the applicable prior art.
The ‘132 patent, owned by appellant Daedalus, relates to a policy-based data management system for handling files.  Regarding the field of endeavor, the Federal Circuit noted that it need not reach this issue, as the PTAB’s finding that Gelb was reasonably pertinent to the problems of the ‘132 patent was sufficient on its own to establish Gelb as analogous art. *Id.* at 4. A reference qualifies as analogous art if it is either “in the same field of endeavor” or “reasonably pertinent to the particular problem with which the inventor is involved.” Donner Tech., LLC v. Pro Stage Gear, LLC, 979 F.3d 1353 (Fed. Cir. 2020).

The ‘132 patent, owned by appellant Daedalus, relates to a policy-based data management system for handling files. In its short opinion, the Federal Circuit did not reach the “field of endeavor” question because it concluded that Gelb was reasonably pertinent to the problems of the ‘132 patent.   In particular, the court concluded that the ‘132 patent identified the problem that prior art systems did not “permit a user to automatically select between multiple storage options” or address “files with varying storage or performance requirements or equipment with varying capacities and performance levels.”  The PTAB found that Gelb addresses the same problem – i.e., prior art storage access methods did not allow programmers to write code enabling users to automatically select appropriate storage devices based on high-level concepts like data sets and databases.  On appeal, the Federal Circuit agreed that substantial evidence supported this PTAB determination.

Although the Daedalus patent focuses on a networked environment, the claims did not expressly require the networked environment. The patentee particularly argued that under a proper claim construction that Gelb was not analogous because that reference focused on a non-network environment.  Kevin McNish, arguing for the patentee made the case at oral argument:

When we’re talking about a distributed system, we’re talking about multiple machines, and these machines are processing instructions, capable of processing instructions, capable of functioning as part of the distributed system or autonomously as well. Contrast that to what we have in Gelb, where, again, we just have these peripheral devices, these being hooked up directly by cables into this centralized single-machine architecture. . . .

So ultimately, what this comes down to is, you know, Gelb, again, single machine, non-networked, centralized architecture, not pertinent to problems in multi-machine networked distributed storage systems in which the invention operates, as reflected by our construction of plurality of clients, as clients in a networked environment.

On appeal, the Federal Circuit rejected this claim construction argument that the term “plurality of clients” should be limited to “clients in a networked environment.” Even under Daedalus’s proposed construction, the court explained, the PTAB’s reasonable pertinence finding would stand, as the storage selection problem identified in the specification was agnostic to whether the clients are networked.  Arguing on behalf of the USPTO, Michael Forman explained the USPTO’s position as follows:

I think if you look at both the specification of the 132 patent and the prosecution history, you can see that the patentee was defining the problem as a data management problem, not as a network problem.

The Federal Circuit agreed with this perspective, that the problem stated was not focused on network issues.  In other words, the patentee’s argument might have worked if the Daedalus patent had expressly identified the problem being solved as focused on storage options “in a networked environment.”

Although the patentee lost this appeal, I believe that it adds to the body of evidence that applicants should consider filing narrower patent specifications when appropriate. In our post-AIA world, patents are more likely than ever to be invalidated post-issuance, and a carefully crafted problem statement can help limit the scope of analogous art. By explicitly identifying the specific problem solved by the invention, particularly in the broadest claims, applicants may be able to circumscribe the universe of prior art that can be relied upon for obviousness. While this approach requires striking a delicate balance to avoid unduly restricting claim scope, it is a strategy worth considering in light of the evolving analogous art doctrine.

Key Takeaways for Patent Prosecutors:

  • Recognize that the AIA changed the post-grant rules.  Today protecting against post-grant obviousness cancellation is often just as important as avoiding narrowing constructions that might hurt the infringement case.
  • In appropriate cases consider explicitly stating the problem solved: Clearly articulating a specific problem addressed by the invention in the specification and claims can potentially limit the scope of analogous art relied upon by the examiner as well as by the PTAB in a post-grant trial.
  • Consider two separate patent families filed concurrently: one with a broad statement of the problem and another with a narrower construction.

= = =

The Donner Tech case includes an interesting footnote that was not contemplated by this decision.

One exception that has been contemplated, but not solidified, by our case law is where the problem a reference solves is so specific to its particular field of endeavor that a PHOSITA could not possibly describe the problem the reference solves other than in a manner that rules out all art outside that field.

Citing Sci. Plastic Prods., Inc. v. Biotage AB, 766 F.3d 1355, 1360 (Fed. Cir. 2014).

31 thoughts on “The Analogous Art Doctrine Post-KSR: Insights from the Federal Circuit’s Daedalus Decision

  1. 7

    I’m curious. The patent in question was written over twenty years ago. There was no AIA, no KSR. Are we confident that, if today we write applications in accordance with these suggestions, those patents will be better suited to survive whatever the law happens to be twenty years from now?

    1. 7.1

      Given that the courts tend to be influenced by the massive propaganda of “bad patents,”


    2. 7.2

      The “survival” of your patent depends to a large extent on what you (or whomever you sell/license it to) intend to do with it.

      Let’s see if the whining patent huffers here can handle the nuance.

    3. 7.3

      That’s why patent prosecutors should take the “advice” of patent litigators with a grain of salt.
      It was a patent litigator that gave us KSR.
      It was a patent litigator that gave us Bilski.
      It was a patent litigator that gave us Alice.
      etc. etc. etc.
      George Taylor: You Maniacs! You blew it up! Ah, damn you! God damn you all to hell!

  2. 5

    OT: What is the historical origin of continuation practice? Did it exist before the 1952 patent act?

    1. 5.1

      quoting Frederico’s commentary on the 1952 Act:

      “Continuing applications (section 120). Under certain circumstances an application for patent is entitled to the benefit of the filing date of a prior application of the same inventor filed in the United States. This was not specified in the old statute but was developed by decisions of the courts beginning with a decision of the Supreme Court of 1864, Godfrey v. Eames, 68 U.S. 317.

      Section 120 of this title is a new section which enacts the right to rely upon the date of a prior application.”

  3. 4

    ” … where the problem a reference solves is so specific to its particular field of endeavor … ”

    What’s good for the goose …

    Fair is fair.

  4. 3

    During patent examination, the Examiner will define the field of endeavor so broadly and generically as to encompass numerous fields, and then either ignore the problem actually solved by the inventor or reformulate the problem being solved by the inventor so generically as to encompass the problem being solved in the reference being cited.

  5. 2

    A few years ago I reviewed a hundred non-analogous art PTAB cases. Most non-analogous art arguments failed because they were obviously wrong, not because of any post-KSR jiggering with the definition of analogous art. Where a reference was outside the field of endeavor (of the applicant’s endeavor) and not pertinent to the problem solved (the applicant’s problem), the non-analogous art argument always prevailed.
    Narrowing the scope of a patent is a good idea for many reasons, not just insulating yourself from far-afield references. Many other reasons not to be a pig. I wonder if you might survive with narrowly focused claims (treatment of a specific breast cancer, for example) in a spec the suggests broader application (treatment of various diseases, generally). I think it would be a tug of war between the narrow field/problem addressed in the claim and the broader field/problem in the spec.

    1. 2.1

      Thanks for this info on your survey a few years ago of a hundred “non-analogous art” PTAB cases, not finding a significant difference made by KSR. This is certainly in contrast to many commenter’s complaints about KSR on this blog [not just re TSM].

      1. 2.1.1

        Most all complaints about KSR are not about the analogous arts condition.

        Put the pom poms down.

      2. 2.1.2

        At one point, Examiners cited KSR as broadening the analogous arts test in relation to the equating the problem being solved by the inventor with the problems being solved by a person of ordinary skill in the context of motivation to combine references.


          That the editors of the MPEP thought that KSR had anything to do with the analogous art issue tells you all you need to know about the editors of the MPEP. The PTO is not sending us their best.

      3. 2.1.3

        Yeah, I agree that it doesn’t match the conventional wisdom. But if you can establish that the field of endeavor is different (like, common sense, CPC classification, different industries, or different “Field of the Invention” statements) and the problem solved is different, you can prevail.
        I always start with the “Field of the Invention.” In my limited experience, a very narrow field of the invention in your own patent is very helpful, even if your spec includes some suggestion of broad application, to establish a different field of endeavor.


          The inventor’s view of stated field of endeavor does not carry a lot of weight.

          This is not Design Patent law…


            Actually, it has proven dispositive in a couple of cases. Don’t sell it short if its in your favor.

    2. 2.2

      I would be interested to know just how many cases found that the art was not “reasonably pertinent to the particular problem addressed by the inventor.”

      In my experience, the “reasonably” modifier expands what art can be considered by the examiner. Is it reasonable to consider the art, even though it is not really pertinent?

      Would one consider the art at all without applicant’s specification in hand?

      In the case at hand, what if the assumption in the art was that what worked with a single, non-networked machine would not translate to a network? So no one tried it, until the inventors? Looking backwards, we can conclude it was reasonably pertinent. But would we do so looking forward from the reference, without applicant’s specification in hand?

  6. 1

    Dennis is suggesting here a practical practice change – that AIA post-grant proceedings [almost entirely IPRs in practice] ought to encourage drafting specifications that can support claims better distinguishing prior art.
    But, I think it is important to note that IPRs are invalidating many claims that would not have survived a [vastly more expensive] full trial and Fed. Cir. appeal before the AIA either.* The practical difference is that before the AIA there was only reexamination as an alternative to invalidation with such costly full blown litigation, and thus more patent suits were settled by paying to avoid such litigation, with NO validity challenge or test of any kind.
    *E.g., here, relying on a non-analogous art argument to prevent prior art from being applied to broad claims is not often successful since KSR [except in design patent litigation] anyway.

    1. 1.1

      Every time I argue non-analogous art in the patent office, I prevail. Because I don’t argue it when it is not going to work. I see so many dumb non-analogous arguments. In my own informal survey of PTAB cases, the only dividing line I saw was good arguments versus dumb arguments. I didn’t see a pre-KSR/post-KSR divide.

      1. 1.2.1

        ? That patent owners [as well as PAEs and other litigation attorneys] could get More cash settlements even on invalid patents Before the AIA supports Anti-IPR views.

    2. 1.3

      Since the burden of proof is so very different, I am not sure the assumption in your second sentence can be made.

      Another issue to consider is that, in fields such as antibodies, there have been no cases finding infringement under the DOE. So, narrowing the claims to a particular problem may be a pyrrhic victory.

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