ABSTRACT
A situation where people control a spontaneously changing situation will here be regarded as consisting of two systems: one a target system (the system to be controlled) and the other a controlling system (comprising people and artifacts whose goal is to control the target system). These two systems are tightly linked, and may be regarded as two sides of a coin. Current analyses tend to concentrate on one or other of the sides, and so it can be advantageous to separate them.
