1. A computer system, comprising: a computer processor; at least one sensor for determining at least one characteristic of 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; (ii) a semantic memory database indicative of the incidence in the previous episodes of each of a plurality of predefined concepts C; and (iii) program instructions operative by the processor to cause the processor to: (a) use data obtained using the at least one sensor to classify a 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) use the current concept set, the episodic memory and the semantic memory to obtain additional information relevant to the current situation, and transmit at least some of the additional information to the user using the at least one information transmission device.