Probabilistic Safety Evaluation of Dynamic Hazard Propagation

GERT can be a suitable tool for probabilistic safety evaluation of dynamic hazard propagation processes because it can deal with logic conditions, probability, and dynamic properties simultaneously. This paper proposes a new method which, assuming that the time parameter of each arc is a discrete variable, can systematically translate a GERT graph with some non Exclusive-OR nodes (eg, Inclusive-OR nodes and AND nodes) into a probability graph where every node is Exclusive-OR. This method first introduces a marked GERT graph which has tokens and delay nodes added to the original GERT graph in order to express the system state. The method then moves tokens in a marked GERT graph, and constructs a state transition graph which consists of only Exclusive-OR nodes. The method is applied to an example to demonstrate its usefulness.