Inventive step is defined in PCT Article 33(3).
PCT Article 33
The International Preliminary Examination
- (3) For purposes of the international preliminary examination, a claimed invention shall be considered to involve an inventive step if, having regard to the prior art as defined in the Regulations, it is not, at the prescribed relevant date, obvious to a person skilled in the art.
PCT Rule 65
Inventive Step or Non-Obviousness
65.1 Approach to Prior Art
For the purposes of Article 33(3), the international preliminary examination shall take into consideration the relation of any particular claim to the prior art as a whole. It shall take into consideration the claim’s relation not only to individual documents or parts thereof taken separately but also its relation to combinations of such documents or parts of documents, where such combinations are obvious to a person skilled in the art.
The above provisions apply mutatis mutandis to the written opinion of the International Searching Authority. See PCT Rule 43bis.1(b).