Human-computer interface evaluation: not user-friendliness but design for operation.

This paper considers human-computer interface evaluation in the context of design and development. It is argued that it is not helpful to view evaluation as a method for achieving user-friendliness, rather it should be seen as a participating activity within design and development. The centre of concern is the operation of the system when employed in practice. Such evaluation is not necessarily to be conducted by independent observation and experiment, but may be closely integrated with other design activities. In fact the very theory underlying the evaluation finds its embodiment in the artifact of the user interface. Taking this view has technical, as well as human factors, implications.