Abstract
Decision-making plays an important role in life-critical systems. It entails cognitive functions such as monitoring, as well as fault prevention and recovery. Three kinds of objectives are typically considered: safety, efficiency and comfort. People involved in the control and management of such systems provide two kinds of contributions: positive with their unique involvement and capacity to deal with the unexpected; and negative with their ability to make errors. In the negative view, people are the problem and need to be supervised by regulatory systems in the form of operational constraints or by design. In the positive view, people are the solution and lead the game; they are decision-makers. The former view also deals with error resistance, and the latter with error tolerance, which, for example, enables cooperation between people and decision support systems (DSS). In the real life, both views should be considered with respect to appropriate situational factors, such as time constraints and very dangerous environments. This is known as function allocation between people and systems. This paper presents a possibility to reconcile both approaches into a joint human-machine organization, where the main dimensioning factors are safety and complexity. A framework for cooperative and fault tolerant systems is proposed, and illustrated by an example in Air Traffic Control.