It must be examined whether the problem defined by reference to the closest prior art has indeed been solved the claimed invention. If not, the problem must be reformulated.

When defining the objective technical problem an effect cannot be retained if it is not credible that the promised result is attainable throughout the entire range covered by a claim (T 741/91; T 626/90; T 939/92, OJ 1996,309; T 583/93, OJ 1996, 496).

If the inventive step of a claimed invention is based on a given technical effect, the latter should, in principle, be achievable over the whole area claimed (T 939/92, OJ 1996, 309; T 694/92, OJ 1997, 408; T 583/93, OJ 1996, 496).