This paper presents an approach to the description and analysis of complex
Man-Machine Systems (MMSs) called Cognitive Systems Engineering (CSE). In c
ontrast to traditional approaches to the study of man-machine systems which
mainly operate on the physical and physiological level, CSE operates on th
e level of cognitive functions. Instead of viewing an MMS as decomposable b
y mechanistic principles, CSE introduces the concept of a cognitive system:
an adaptive system which functions using knowledge about itself and the en
vironment in the planning and modification of actions. Operators are genera
lly acknowledged to use a model of the system (machine) with which they wor
k. Similarly, the machine has an image of the operator. The designer of an
MMS must recognize this, and strive to obtain a match between the machine's
image and the user characteristics on a cognitive level, rather than just
on the level of physical functions. This article gives a presentation of wh
at cognitive systems are, and of how CSE can contribute to the design of an
MMS, from cognitive task analysis to final evaluation.