The patentability of software, computer programs and computer-implemented inventions under the European Patent Convention (EPC) is the extent to which subject matter in these fields is patentable under the Convention on the Grant of European Patents of October 5, 1973. The subject also includes the question of whether European patents granted by the European Patent Office (EPO) in these fields (sometimes called "software patents") are regarded as valid by national courts. Under the EPC, and in particular its Article 52, "programs for computers" are not regarded as inventions for the purpose of granting European patents, but this exclusion from patentability only applies to the extent to which a European patent application or European patent relates to a computer program as such. As a result of this partial exclusion, and despite the fact that the EPO subjects patent applications in this field to a much stricter scrutiny when compared to their American counterpart, that does not mean that all inventions including some software are de jure not patentable. The European Patent Convention (EPC), Article 52, paragraph 2, excludes from patentability, in particular discoveries, scientific theories and mathematical methods; aesthetic creations; schemes, rules and methods for performing mental acts, playing games or doing business, and programs for computers; [emphasis added] presentations of information. Paragraph 3 then says: The provisions of paragraph 2 shall exclude patentability of the subject-matter or activities referred to in that provision only to the extent to which a European patent application or European patent relates to such subject-matter or activities as such." [emphasis added] The words "as such" have caused patent applicants, attorneys, examiners, and judges a great deal of difficulty since the EPC came into force in 1978. The Convention, as with all international conventions, should be construed using a purposive approach. However, the purpose behind the words and the exclusions themselves is far from clear.