W 0017/03 (Radio frequency identification/3M) of 20.09.2004

Invitation to pay additional fees sufficiently reasoned (yes)
Investigation of technical relationships with the aid of common problems underlying the inventions

1. The evaluation of unity involves comparing problems solved (or effects achieved) by different claims, whereas the evaluation of inventive step is carried out on a single claim. As a result, when examining unity, the problems solved by different claims must be considered in the light of each other and cannot be determined in isolation in an absolute sense.
2. In the evaluation of inventive step, the idea is to define a problem based on the distinguishing features that is essentially as narrow as possible, but not involving elements of the solution. On the other hand, in the evaluation of unity, these restrictions do not apply, since the overall object is to find out what the claims have in common, i.e. if the respective inventions are so linked as to form a single general inventive concept.
3. Hence, the specific problems solved by the different inventions with respect to the closest prior art may need gradual refinement, in particular generalisation starting from the problems directly solved, to find out whether or not there is a common denominator that still distinguishes the inventions from said prior art (see reasons 3.3 to 3.5).