1. A method of obtaining information relevant to a current situation, the method being performed by a computer system comprising: a computer processor; at least one sensor for determining at least one characteristic of the user, at least one data input device for receiving input from the user; at least one information transmission device for transmitting information to the user; and a data storage device, the data storage device storing: (i) an episodic memory database of documents, each document representing a respective previous episode experienced by the user; and (ii) a semantic memory database indicative of the incidence in the previous episodes of each of a plurality of predefined concepts C; the method comprising: (a) using data obtained using the at least one sensor to classify the current situation according to the plurality of predefined concepts C, to derive a current concept set which is one or more of said predefined concepts C, the current concept set being those of the predefined concepts C which are relevant to the current situation; and (b) using the current concept set, the episodic memory and the semantic memory to obtain additional data relevant to the current situation wherein the method further comprises a preliminary step of generating the semantic memory by: classifying the documents in the episodic memory according to the predefined concepts C to determine a sub-set of the predefined concepts relevant to each of the documents, and for each document, updating the semantic memory according to the corresponding derived sub-set of the predefined concepts.