The search should on the one hand not be restricted to the literal wording of the claims, but on the other hand should not be broadened to include everything that might be derived by a person skilled in the art from a consideration of the description and drawings. The objective of the search is to discover prior art which is relevant to novelty and/or inventive step (see II, 2). The search should be directed to what appear to be the essential features of the invention and take into account any changes in the (objective) technical problem underlying the invention which may occur during the search as a result of the retrieved prior art (see IV, 2.3, IV, 2.4 and C-IV, 11.7.2). In this regard it should be noted that although explicit references in the claims to features elucidated in the description are only permissible where "absolutely necessary" (Rule 43(6) - see also III, 3.5, and C-III, 4.17), claims containing such references should still be searched if these technical features are unambiguously defined by specific parts of the description.

When interpreting claims for the purpose of the search, the search will also take into consideration prior art incorporating technical features which are well known equivalents to the technical features of the claimed invention, which may undermine inventive step (see C-IV-Annex, 1.1(ii) ).