In the second stage, the examiner establishes in an objective way the technical problem to be solved. The method to do so is to study the application (or the patent), the closest prior art and the difference (also called "the distinguishing feature(s)" of the claimed invention) in terms of features (either structural or functional) between the claimed invention and the closest prior art, identify the technical effect resulting from the distinguishing features, and then formulate the technical problem.
The objective technical problem derived in this way may not be what the applicant presented as "the problem" in the application. The latter may require reformulation, since the objective technical problem is based on objectively established facts, in particular appearing in the prior art revealed in the course of the proceedings, which may be different from the prior art of which the applicant was actually aware at the time the application was filed. In particular, the prior art cited in the search report may put the invention in an entirely different perspective from that apparent from reading the application only. Reformulation might lead to the objective technical problem being less ambitious than originally envisaged by the application.
Section GL/EPO G‑VII, 5.2, in the Guidelines for Examination in the EPO applies mutatis mutandis.