Once the search reveals prior art, which discloses or renders obvious the technical problem stated by the applicant under Rule 42(1)(c) as underlying the application, the fulfilment of the requirements of unity of invention may be (re)assessed a posteriori (see also F-V, 6). This is because although the technical problem stated by the applicant is still a single general concept, it can no longer be regarded as being inventive, i.e. it cannot constitute the single general inventive concept required by Art. 82.
For example, a prior-art document under Art. 54(2) disclosing all the features of an independent claim also discloses, at least implicitly, the technical problem stated by the applicant, since by definition this problem must be solved by the features of said independent claim.
As a general rule, the next steps consist of assessing which claims are new and non-obvious compared with the relevant prior art available at the moment the application is examined for the requirement of unity. "Remaining claims" are the claims that still appear to be new and non-obvious after this assessment.
The examiner will then proceed to analyse if any special common matter in the sense of Rule 44(1) is present in these remaining claims, i.e. identify, in the light of the application as a whole, any technical features of the remaining claims that are the same or corresponding.
If any of the remaining claims contain one or more alternatives, each of the alternatives is considered as a single claim for the purpose of assessing lack of unity.
The principles of the problem-solution approach are to be applied when determining if, in view of the entire application as filed, some of the technical features of the remaining claims are corresponding, i.e. if they solve the same technical problem and hence form part of the common matter.
In particular, in the case of features defining technical alternatives, if the common technical effect to be achieved is already known, or may be recognised as generally desirable (a mere desideratum), or is obvious, these alternative features are not considered as defining a technical relationship in the sense of Rule 44(1) because there is no inventive merit in formulating the problem (T 2/83).
If common matter is identified and, in the light of the prior art at hand, comprises any same or corresponding technical features that appear to contribute to the achievement of at least one new technical effect in a non-obvious way, then these features define a technical relationship between the remaining claims in the sense of Rule 44(1), and the requirements of unity of invention are fulfilled.
If either no common matter can be identified or the identified common matter is known or obvious from the known prior art, then the application lacks unity because neither a technical relationship in the sense of Rule 44(1) is present between the remaining claims, nor does the application entail a single general inventive concept in the sense of Art. 82.
If the application is found to lack unity, some of the remaining claims may still share same or corresponding special technical features. The remaining claims are thus grouped into inventions according to what same and/or corresponding special technical features they have in common.