Problems behind inventive step

The inventive step criterion is usually the center point of most contestable patentability examinations (there are of course many inventions which are incontestably not patentable, and some which are incontestably patentable). When the applicant writes an application, the true extent and content of previously published inventions in the same technological field is more or less unknown. The examination process is normally a comprehensive search for prior art documents which have hitherto been unknown to the applicant. Once the closest prior art documents have been found, the patent examiner gives an opinion on whether or not the claimed invention meets the requirement of inventive step in view of the prior art.

The public benefits of the patent system require that patent monopolies be restricted. In particular, patents should not be granted to claimed inventions whose differences with regard to the prior are nonexistent or technically insignificant. It makes no difference whether or not the applicant was actually aware of any particular prior art document when the application was filed. The applicant cannot, for example, argue that a Japanese prior art document which matches her invention claimed should be disregarded, because she does not understand Japanese. Her defense may be truthful, but she loses the patent due to the unfortunate coincidence that a Japanese person made the same invention before her. In order to prevent copycats from receiving patent monopolies, patents must be granted only to inventions which could not have be reached through minor modifications from any previously published document – no matter how unlikely it may be that the applicant would in reality have read and copied this precise document.

Although the inventive step criterion is clear in abstract form (“grant only those applications which exhibit a significant difference over the prior art”), it is difficult to apply in practice. It is difficult for a patent examiner to decide, on any quasi-objective scale, where the line between significant and insignificant differences should be drawn. For a long time, patent examiners based these decisions primarily on their personal judgment and past experience, comparing each new case to decisions they had made earlier. This method was not as arbitrary as it may sound. Experienced examiners could most probably apply their personal experience fairly to new applications when they set their mind to it. However, it was very hard to ensure that this informal way of applying the inventive step criterion remained constant, or even comparable, between different examiners. Another problem with personal judgment was that it usually involved fairly little explicit reasoning which could be put in writing. Decisions which were based purely on personal judgment tended to be opaque to an outside audience, including the applicant who received the decision.

In the past 25-30 years, especially at the European Patent Office, the influence of examiner’s personal judgments has been reduced, and been made more explicit, by consistently judging the inventive step criterion through a theoretical framework. With the help this framework examiners can split their decision process into logical parts and exercise critical reflection on each part. This so-called problem-solution framework is the only attempt to formulate a general theory of inventive step. The benefits of a more theoretical approach is that it promotes clear and legible argumentation and helps examiners avoid hindsight fallacies.

Problems and their solutions

The problem-solution approach can be studied best through the case law of the European Patent Office. Very briefly, it involves a comparison between one patent claim and one document (usually the document which has been deemed the closest prior art). The claim comprises a list of technical features. One by one, the examiner checks which features are directly disclosed in the document (either explicitly or implicitly). The examiner then focuses on the remaining features (the ones not disclosed in the document) and asks what their combined technical effect (over the prior art disclosed in the document) is. In other words, what technical  benefit, which is not achieved in the same in the closest prior art document, is achieved through these features. A clear benefit is not a necessary requirement under all circumstances, but it is easier to understand the problem-solution method in these terms.

If no beneficial technical effect can be discerned, the claim clearly lacks an inventive step over the prior art document and the decision is clear. But if there is a beneficial technical effect, the examiner then seeks to formulate the technical problem which a person skilled in the art would have had to solve, when reading the prior art document on the day when the application was filed, to achieve the benefit which the invention achieves.

Instead of asking whether or not it would have been obvious to a person skilled in the art that the undisclosed features produce the beneficial technical effect (a question which involves a hindsight fallacy), the examiner instead thinks about the general improvement which the person skilled in the art may have sought to make to the prior art document, and asks whether or not the person could have solved the problem pertaining to that improvement by adding the undisclosed features to the apparatus known from the document.

The applicant has usually presented some technical problem pertaining to the invention in the application. A basic consequence of problem-solution analysis is that this so-called subjective problem may not be relevant. The examiner may, for example, discover a closest prior art document where those features which the applicant presumed to be unknown in the prior art are in fact disclosed. Features which the applicant assumed to be known in the prior art, may on the other hand not be known from this document. This means that the so-called objective technical problem, which the examiner (or anyone else) formulates after a closest prior art document has been discovered, may differ significantly from the subjective problem which the applicant assumed to be most relevant for the invention.

The objective technical problem

Although the problem-solution approach provides a theoretical framework for assessing inventive step, the examiner (or any other person who might make use of it) is still left with a lot of discretion in applying it. There are no comprehensive guidelines concerning how the objective technical problem should be formulated. The guidelines published by the EPO state merely that the general form of the problem should be “how to modify or adapt the closest prior art to achieve the technical effect(s) which the invention provides over the closest prior art”.

An very important addition to this guideline is provided in section I.D.4.3.1 of the Case Law of the EPO Boards of Appeal: “the problem should be as specific as possible without containing elements or pointers to the solution”. In the following sections I will examine what this means.

Two important questions arise from the general for of the problem (cited above) and from the above guideline: (1) how should the closest prior art be conceived if the problem is to be as specific as possible without containing pointers to the solution, and (2) how should the technical effect(s) be conceived if the problem is to be as specific as possible without containing pointers to the solution?

The closest prior art

Question (1) may at first seem nonsensical. A prior art document is what it is, fixed and unchangeable. There may seem to be very little room for free interpretation when a person skilled in the art reads the closest prior art document in full and sets out to make improvements by solving problems pertaining to the document.

However, the definitions in a patent claim are usually made in general terms. This means that the apparatus or method described in the prior art document may in fact differ from the claimed apparatus or method, even though it possesses the claimed features.

For example, let’s imagine mirrors with two kinds of shapes: convex-shaped mirrors and convax-shaped mirrors (the latter concept is my own invention). Convex and convax shapes have some similarities, but also certain differences. Let’s also imagine that the terms “convex” and “convax” are well-established for conceptualizing their differences. In other words, most practitioners in this field of technology know what the difference between a convex shape and a convax shape is.

Furthermore, let’s assume that the additional term “convux” (also my own invention) has conventionally been used to conceptualize the similarities between convax and convex shapes. In other words, “convux-shaped” is used as a general term to cover both convex-shaped and convax-shaped mirrors, and possibly other shapes as well. This means that all convex mirrors are convux mirros and all convax mirrors are also convux mirrors.

Now, let’s imagine that inventive step is assessed on a patent claim which contains a feature F1 which defines a convux mirror, and that the closest prior art document discloses convax mirror. The patent claim we are imagining may be included in a patent application which discusses convex mirrors, or one which which discusses only convux mirrors – this makes no difference for the argument which follows.

Our imaginary patent claim specifies only the general term “convux”, but the prior art relates to a more specifically defined “convax” mirror. The prior art mirror certainly falls into the scope of the claim, even though the category “convax” does not exhaust the category “convux”.

In this case, conceiving the closest prior art “as specifically as possible” means that the convax mirror in the prior art document must be conceived as a convux mirror, not as a convax mirror.

Let’s imagine that the patent claim mentioned above also specifies features F2 and F3, and that F2 is disclosed in the prior art document, while F3 is not.

Feature F3 produces a technical effect which solves a general problem P, which is common to all convux mirrors. This problem may be more difficult than the corresponding subproblem P’ which pertains specifically to convax mirrors. For example, some properties of convax mirrors may make the problem P’ fairly small and easy to solve, while other properties of convex mirrors may make the corresponding subproblem P” for these types of mirrors much more difficult.

In this case “the closest prior art” must therefore specifically be conceived as a convux mirror, not a convax mirror. The scope of the problem P may not be the same as the scope of either subproblem P’ or P”. A correct formulation of the objective technical problem must take this into consideration.

To summarize, we might say that in the objective technical problem the prior art should be designated with the most specific term which fits both the claim and the prior art. In this case, that term is “convux”.

The technical effect

Question (2), how should the technical effect(s) be conceived if the objective technical problem is to be as specific as possible without containing pointers to the solution, is simpler. The technical effect of a claimed feature F (which is not disclosed in the closest prior art document) can generally be described in two different ways:

(A) a detailed description of the changes which take place in the apparatus/method itself, and/or in the surroundings on which it operates, due to F.

(B) a general description which specifies the property (in the apparatus/method, or in its surroundings) which is changed due to F.

A detailed description (A) may specify various parts of the apparatus and how they interact both with each other and with their surroundings. A general description (B) instead specifies a property such as quality, performance, efficiency, cost, durability, yield, storage requirements, versatility, user-friendliness, etc.

A clear way to state the technical effect of a claimed feature F is that this property changes because this happens in the method/apparatus or their surroundings. Or, in the shorthand notation introduced above: B because A.

With these distinctions in mind, the answer to question 2 is this: in the objective technical problem, the technical effect must always be conceived only as a general description B. Any attempt to include the detailed description A in the technical problem would be a pointer to the solution. The problems that a person skilled in the art may identify in the closest prior art document have to do with general properties which could be improved. After noticing a property which could be improved, the person skilled in the art may get down to the details. But the crucially important line between as specific as possible and no pointers to the solution lies precisely after the moment when a problem has been noticed on a general level.

In other words, a problem should be general and should not contain any details which pertain to its solution. Including in the objective technical problem any detailed descriptions (A) would lower the bar too much in the inventive step criterion, because a pointer to the solution would then be included in the problem itself. That is why the objective technical problem must always state the technical effect of a feature F as a general description (B).


This essay demonstrates that the objective technical problem, usually formulated as “how to modify or adapt the closest prior art to achieve the technical effect(s) which the invention provides over the closest prior art” must be formulated and interpreted very carefully if it is to be “as specific as possible without containing elements or pointers to the solution”.

The objective technical problem is the fulcrum around which the inventive step criterion revolves in European patent practice. Fair decisions on inventive require careful considerations of the objective technical problem by practitioners who apply the problem-solution approach.








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