The "state of the art" for the purposes of considering inventive step is as defined in Art. 54(2) (see G-IV, 1). It is to be understood as concerning such kind of information as is relevant to some field of technology (see T 172/03). It does not include later published European applications referred to in Art. 54(3). As mentioned in G-IV, 3, "date of filing" in Art. 54(2), means date of priority where appropriate (see F-VI). The state of the art may reside in the relevant common general knowledge, which need not necessarily be in writing and needs substantiation only if challenged (see T 939/92).