In German court decisions as well as in the German patent literature it has been a generally accepted position that product claims on the one hand and process claims on the other hand represent distinct claim categories; and that product patents (containing only product claims) and process patents (containing only process claims) are distinct patent categories. The applicant is free to choose the appropriate claim category or categories; a patent may contain product claims, process claims or both. However, after grant this choice is binding on the patentee, and a change of category from a product patent to a process patent (and vice versa) is considered to be inadmissible because it involves an extension of the protection conferred (Benkard, Patentgesetz – Gebrauchsmustergesetz, 9th Edition 1993, pages 141, 501, 686 and 710).
