Art. 84 EPC provides that the purpose of the claims is to define the matter for which protection is sought. It lays down the relevant principles governing the content and wording of the claims, providing that claims should be clear and concise and be supported by the description. It is supplemented by R. 43 EPC, which requires inter alia that the claims "shall define the matter for which protection is sought in terms of the technical features of the invention".
The Enlarged Board explained in decision G 2/88 (OJ 1990, 93, Corr. 469) that the primary aim of the wording used in a claim must be to satisfy the requirements under Art. 84 and R. 29(1) EPC 1973 (R. 43(1) EPC), having regard to the particular nature of the invention, and the purpose of the claims. The purpose of claims under the EPC is to enable the protection conferred by the patent or patent application to be determined (Art. 69 EPC), and thus the rights of the patent owner within the designated contracting states (Art. 64 EPC), having regard to the patentability requirements of Art. 52 to 57 EPC.
The boards of appeal have repeatedly confirmed that claims had to be clear for the sake of legal certainty, as their purpose was to enable the protection conferred by the patent to be determined (see e.g. T 337/95, OJ 1996, 628; T 586/97, T 437/98, T 728/98, OJ 2001, 319; T 877/99, T 1074/00, T 560/09).