Introduction

The most challenging judgment in patentability search is not Novelty, but Inventive Step, and the problem-solution approach is the most widely used framework for structuring that judgment. Novelty is relatively “mechanical” — find a Prior Art Document and compare whether there exists an identical technical solution. Inventive Step, however, involves subjective judgment: is the invention “obvious” to a Person Skilled in the Art?

In international patent examination practice, the core methodology for assessing Inventive Step is the “Problem-Solution Approach” established by the European Patent Office (EPO) — this is the common language shared by EPO examiners, patent attorneys worldwide, patentability searchers, and opponents alike. This article breaks down the key operational points of each step of the Problem-Solution Approach, helping you master the most critical intellectual judgment in patentability search.

Legal Basis for Inventive Step Assessment

According to EPC Art. 56, an Inventive Step means that, having regard to the Prior Art, the invention is not obvious to a Person Skilled in the Art.

• Non-obviousness: To a Person Skilled in the Art, the invention must be non-obvious relative to the Prior Art. If, after applying the Problem-Solution Approach, you find that “this solution is quite easy to think of” — there is a problem with Inventive Step.
• Person Skilled in the Art: A legal fiction — an ordinary practitioner who is aware of all common technical knowledge in the relevant field before the Filing Date, but who possesses no inventive capability whatsoever.

The Problem-Solution Approach in Detail

Step 1: Determine the Closest Prior Art

The Closest Prior Art is the starting point and anchor of the entire Inventive Step analysis. Choosing the wrong starting point will skew the subsequent analysis.

What is the “Closest”?

The Closest Prior Art refers to the technical solution in the Prior Art that is most closely related to the claimed invention. It can generally be assessed along the following dimensions:

Dimension 1: Same or Similar Technical Field
Prioritize Prior Art Documents that belong to the same or a similar technical field as the invention. Selecting a cross-field document as the “Closest Prior Art” is only an option when no document from the same field can be found.

Dimension 2: Same or Similar Technical Problem
Does the Prior Art Document attempt to solve the same or a similar technical problem?

Dimension 3: Discloses the Most Technical Features
How many technical features of the invention does the Prior Art Document disclose? The more disclosed, the closer it is.

Dimension 4: Closest Technical Effect
Is the technical effect achieved by the Prior Art Document of the same order of magnitude or type as that of the claimed invention?

Common Mistakes in Selecting the Closest Prior Art:

• Selecting the “worst” Prior Art: Choosing a Prior Art Document that discloses the fewest technical features, so as to make the “distinctions” of the invention appear greater. This is a typically unprofessional practice and will not be accepted by examiners.
• Selecting a cross-field document: Although cross-field citations may sometimes be used to argue Inventive Step, as the starting point of the “Closest Prior Art,” a document from the same field should be preferred.
• Overlooking that the examiner may select a different “closest” art: In patentability search, it is advisable to conduct Problem-Solution Approach analyses for 2–3 candidate “Closest Prior Art” documents respectively, to see whether different starting points lead to different conclusions.

Step 2: Determine the Distinguishing Technical Features and the Objective Technical Problem Actually Solved by the Invention

Determining the Distinguishing Technical Features

Compare the claimed technical solution with the closest prior art analysis identified in Step 1, and identify the Distinguishing Technical Features between them.

Distinctions exist not only in technical means but also in technical effects — if the invention achieves an effect not achieved by the Prior Art Document, this also serves as evidence of distinction.

Determining the Objective Technical Problem Actually Solved by the Invention

This step is the most prone to deviation. The key principle is: do not directly copy the technical problem originally claimed by the inventor; instead, re-determine the “objective” technical problem actually solved by the invention, based on the technical effect achieved by the Distinguishing Technical Features.

If the technical effect of the invention is exaggerated in the original disclosure, it should be re-assessed based on objective technical features and effects during patentability search.

Step 3: Assessing Obviousness

This is the most difficult part of the judgment in the problem-solution approach. The core question is:
Does the Prior Art as a whole contain some kind of “Technical Teaching” that would motivate a Person Skilled in the Art, when faced with the objective technical problem, to apply the Distinguishing Technical Features to the Closest Prior Art so as to arrive at the claimed invention?

The following circumstances are generally considered to provide a Technical Teaching:

Scenario 1: The Distinguishing Feature Is Disclosed in Another Prior Art Document, and That Other Document Teaches Its Use for the Same Purpose

For example:

• D1 (closest) discloses a heat dissipation device using metal heat sinks
• The claimed invention uses a graphene thermal film to replace the metal heat sink
• D2 discloses that “graphene has excellent thermal conductivity and can be used for heat dissipation in electronic devices”
  → A Person Skilled in the Art would be motivated to replace the metal heat sink in D1 with the graphene taught by D2 → Technical Teaching exists

Scenario 2: The Distinguishing Feature Belongs to Common General Knowledge in the Art

Common General Knowledge refers to Customary Means for solving that technical problem in the art, or conventional technical means recorded in textbooks or technical dictionaries.

If the substitute feature is one of the routine options in the art for solving the technical problem, a Technical Teaching is generally deemed to exist.

Scenario 3: The Distinguishing Feature Can Be Obtained Through Logical Analysis, Reasoning, or Limited Experimentation

If, starting from the Closest Prior Art, the ways to solve the technical problem are limited and predictable, and can be obtained through routine reasoning or simple experimentation — a Technical Teaching may exist.

Circumstances That Do Not Constitute a Technical Teaching:

• “Teaching Away” exists: Other documents explicitly state “do not do this” — in such cases no Technical Teaching exists
• The invention produces an “Unexpected Technical Effect”: The effect substantially exceeds the scope of routine predictability — Inventive Step is strengthened
• After combining the Prior Art Documents, there is technical incompatibility, or additional modifications beyond what a Person Skilled in the Art would reasonably expect would be required to achieve the invention

Practical Case Study of the Problem-Solution Approach

Invention: A battery thermal management method for an electric vehicle, characterized in that: when the battery temperature is detected to exceed a first threshold, a liquid cooling system is activated; when a higher second threshold is exceeded, air-cooling auxiliary heat dissipation is simultaneously activated.

Step 1 — Determine the Closest Prior Art:
Select D1: Discloses a battery thermal management method for an electric vehicle, using a liquid cooling system that activates when the temperature is too high.

Step 2 — Determine the Distinguishing Features and the Objective Technical Problem Actually Solved:

• Distinguishing Feature: Adding a second threshold, above which air-cooling auxiliary heat dissipation is activated
• Objective Technical Problem Actually Solved: Providing additional heat dissipation capacity under extreme high-temperature conditions, preventing a single liquid cooling system from being unable to meet the demand

Step 3 — Assess Obviousness:
D2 discloses a heat dissipation solution for data center servers, where both liquid cooling and air cooling are activated simultaneously when the temperature exceeds a threshold. The question is: would a Person Skilled in the Art be motivated to apply the dual-mode heat dissipation concept of D2 to the battery thermal management of D1?

Analysis:

• The technical fields are similar (both are thermal management of electronic devices)
• D2 explicitly teaches that “under extreme thermal loads, multi-mode heat dissipation is more effective than a single mode”
• Battery thermal management and server thermal management face similar “peak thermal load” challenges
• No “Teaching Away” or technical incompatibility exists

Assessment: To a Person Skilled in the Art, applying the multi-mode heat dissipation concept of D2 to the battery thermal management solution of D1 would be obvious. Inventive Step is questionable.

If the inventor believes no Technical Teaching exists, possible breakthrough points:

• An Unexpected Technical Effect was discovered during experimentation: the combined action of air cooling and liquid cooling on the upper and lower surfaces of the battery produced a cooling effect exceeding expectations (e.g., a synergistic effect exists)
• The solution in D2 requires additional hardware conditions, while the claimed invention achieves the same without adding hardware

Secondary Considerations

Even if the problem-solution approach initially indicates “lack of Inventive Step,” the following secondary factors may reverse the conclusion:

Factor 1: Unexpected Technical Effect
The effect of the invention substantially exceeds the scope of routine predictability. This factor carries significant weight in EPO examination practice.

Factor 2: Overcoming Technical Prejudice
The invention solves a problem that the industry has long considered “infeasible” or “should not be done this way.”

Factor 3: Commercial Success
Commercial success attributable to the technical feature rather than marketing or monopoly — persuasive but relatively difficult to prove.

Factor 4: Long-Felt But Unresolved Technical Problem
The problem has existed for a long time and multiple attempts in the industry have failed; only the claimed solution has solved it.

Common Mistakes in Inventive Step Assessment

Mistake 1: Hindsight Bias

After learning of the invention, looking “back” at the Prior Art makes everything seem obvious. This is the most dangerous cognitive bias in Inventive Step assessment. Always adopt the perspective of a Person Skilled in the Art before the Filing Date. Teams can use PatSnap Analytics to organize prior art, technical features, and comparison records when applying inventive step analysis.

Mistake 2: Excessively Fragmenting the Prior Art

Denying Inventive Step by combining Feature 1 from Document A + Feature 2 from Document B + Feature 3 from Document C + Common General Knowledge — this kind of “mosaic” approach is generally not accepted unless there is a clear “teaching–motivation–reasonable expectation of success” chain.

Mistake 3: Ignoring the Independent Significance of “Unexpected Technical Effect”

Even if obviousness under Step 3 of the Problem-Solution Approach is questionable, if the invention brings about a significant, quantifiable improvement in technical effect that is not linearly predictable (i.e., an “Unexpected Technical Effect”), this can independently support Inventive Step.

Key Takeaways: The core of Inventive Step assessment is the problem-solution approach — (1) determine the Closest Prior Art, (2) determine the Distinguishing Technical Features and the Objective Technical Problem, (3) assess obviousness. Circumstances in which a Technical Teaching exists include: the Distinguishing Feature is disclosed in another Prior Art Document for the same purpose, belongs to Common General Knowledge, or can be derived through logical reasoning and limited experimentation. Secondary Considerations (Unexpected Technical Effect, overcoming Technical Prejudice, etc.) may reverse the preliminary conclusion. Beware of Hindsight Bias. For repeatable patent review workflows, PatSnap Analytics can help teams connect search results with claim comparison and reporting.