In Probabilistic Risk Management, risk is characterized by two quantities:
the magnitude (or severity) of the adverse consequences that can potentially
result from the given activity or action, and by the likelihood of occurrence
of the given adverse consequences. But a risk seldom exists in isolation: chain
of consequences must be examined, as the outcome of one risk can increase the
likelihood of other risks. Systemic theory must complement classic PRM. Indeed
these chains are composed of many different elements, all of which may have a
critical importance at many different levels.