A new definition of complexity in a risk analysis setting

In this paper, we discuss the concept of complexity in a risk analysis context. Inspired by the work of Johansen and Rausand, a new perspective on complexity is presented which includes several common definitions of complexity as special cases. The idea is to link complexity to activities, to the knowledge about the activity and its consequences (including scenarios, events, outcomes), and to the knowledge about the sub-activities: an activity is considered complex if we have poor knowledge about the consequences of the activity, even if we have strong knowledge about the consequences of its sub-activities. In the paper, we show how this perspective provides new insights about the complexity concept and related risk understanding, risk assessment and risk management. The perspective allows in particular for novel ways of characterizing the risk of complex systems and activities. Some examples are used to illustrate the perspective and the discussion.