THE PROBLEM Human-computer interaction (HCI) has been defined (SIGCHI, 1992) as "a discipline concerned with the design, evaluation and implementation of interactive computer systems for human use and with the study of major phenomena surrounding them". In practice, most work in the area is directed towards the human-computer interface, with the object of determining how best to exchange information between a person and an inanimate entity, hardware or software, which will henceforth be referred to as the machine.
