The Rule: A §103 Reference Must Be Analogous Art
There is a real legal doctrine behind the instinct that an examiner should not freely combine technology from anywhere. MPEP § 2141.01(a) states that a reference used in a §103 obviousness rejection must be analogous art to the claimed invention. A nonanalogous reference is not a proper basis for the rejection.
The difficulty is that the test is broader than “same industry” or “same patent classification.” A reference is analogous art if either of two tests is satisfied:
- the reference is from the same field of endeavor as the claimed invention, even if it addresses a different problem; or
- the reference is reasonably pertinent to the problem faced by the inventor, even if it comes from a different field of endeavor.
The reference does not need to satisfy both. That is why a response that simply says “Reference B is from medical devices, while this application concerns industrial machinery” often fails to engage the examiner’s actual legal basis.
Test One: Define the Field of Endeavor with Structure and Function
The field-of-endeavor inquiry is not limited to the narrow label an applicant would prefer to put on the invention. The USPTO instructs examiners to consider the application’s description of the subject matter, including embodiments, function, and structure. Federal Circuit cases likewise reject definitions that are artificially narrowed to the precise point of novelty.
A stronger response therefore does more than compare industry names. It explains why the claimed invention and the reference operate in materially different technical environments, solve different engineering constraints, use different structures, or depend on conditions that a person of ordinary skill would not reasonably treat as part of the same endeavor.
Patent classifications may support the argument, but MPEP § 2141.01(a) warns that similarities and differences in structure and function generally carry more weight than classification labels.
Test Two: Reasonable Pertinence Turns on the Inventor’s Problem
The second test is often where a “different field” argument breaks down. A reference outside the field can still be analogous if it is reasonably pertinent to the problem the inventor faced—meaning that a person of ordinary skill would logically have consulted the reference when confronting that problem.
This makes the definition of the problem critical. If the problem is framed too broadly, almost any reference can begin to look relevant. “How to connect two components,” for example, is much broader than “how to maintain a sealed electrical connection under repeated thermal cycling in a compact battery enclosure.”
In Sanofi-Aventis Deutschland GmbH v. Mylan Pharmaceuticals Inc., the Federal Circuit reviewed an analogous-art dispute involving a reference from a distinct field. The case illustrates why the problem cannot simply be defined at whatever level of generality favors one side. The analysis must be grounded in the specification and in what a skilled person would understand the inventor to have been addressing.
The specification can matter years later to analogous-art analysis. A well-framed technical problem, grounded in the actual engineering constraints of the invention, can make it harder to redefine the problem at an unhelpfully abstract level.
How to Build a Better Nonanalogous-Art Response
If the facts support the argument, a persuasive response should usually address both analogous-art paths rather than stop at a field label.
1. Identify the examiner’s implied field of endeavor
State the field supported by the application’s structure, function, embodiments, and technical context. Then explain specifically why the cited reference falls outside that field.
2. Identify the actual problem faced by the inventor
Use the specification and the claimed technical relationships. If the Office Action has framed the problem too broadly, say why that framing removes the constraints that actually drove the invention.
3. Explain why a skilled person would not have consulted the reference
Focus on engineering logic: incompatible operating conditions, materially different objectives, different structures, or a teaching that would not help solve the identified problem. “Different use” is weaker than “the reference’s solution depends on conditions absent from—and inconsistent with—the claimed system.”
4. Avoid relying on classification alone
Different CPC/USPC classes, product markets, or industry names can be supporting evidence, but they are rarely the strongest evidence. Structure, function, and the problem faced by the inventor are more important.
Do Not Let the Analogous-Art Argument Become the Only §103 Argument
Even a good nonanalogous-art argument should not distract from other defects in the rejection. A complete §103 response may also need to address whether every claim limitation is actually taught, whether there is a reason to combine the references in the claimed manner, whether the proposed modification would change the principle of operation, whether a skilled person would have had a reasonable expectation of success, or whether the references teach away from the combination.
There is another common mistake worth avoiding: when multiple references are used, they do not need to be analogous to each other. Each reference must be analogous to the claimed invention. Attacking the relationship between Reference A and Reference B without tying the analysis back to the claimed invention can therefore miss the governing test.
The Takeaway
“This reference is from a different field” can be the start of a strong §103 response, but only when it is converted into the legal and technical language of analogous art. The better question is whether the reference belongs to the same field of endeavor or would reasonably have commended itself to a skilled person trying to solve the inventor’s problem.
For Chinese-originated U.S. applications, this is also a drafting lesson. The more clearly the original specification explains the technical context, constraints, and problem being solved, the more material exists later to resist an examiner’s overbroad reconstruction of the invention.