This paper considers the abstract features of human/machine interactio
n systems that are required for the production of intelligent behaviou
r. A conceptual architecture is proposed for a subset of intelligent s
ystems called human-centred intelligent systems (HCISs) and it is argu
ed that such systems must be autonomous, robust and adaptive in order
to be intelligent. Soft computing is proposed as a promising new techn
ique that can be used to build HCISs, and examples are presented where
this is already being done. Finally, flexibility is defined to be a c
ombination of the often-conflicting requirements of robustness and ada
ptability, and it is argued that the right balance between these two f
eatures is necessary to achieve intelligent behaviour.