3. Main assumptions and mathematical bases of ADD

From a mathematical point of view, an ADD is an acyclic directed graph, i.e. between the inputs (primary events) and the output (undesired event), it has no loops or feedbacks. It is based on the following fundamental assumptions:

1. the system has only two states, e.g. on/off, and the undesired event at the top of the tree generally corresponds to the system's failure state;

2. the system components have only two states, e.g. on/off, and the primary events generally correspond to the failure states of the components;

3. the ADD represents the logical function linking the primary events to the undesired event. That is, in general, the failure state of the system to the failure states of its components;

4. the primary events are independent of each other....