Conversion from FTA to BDD
The size of a BDD depends on several Boolean variables. An
adequate ranking of basic events is crucial in order to reduce the
size of the BDD, and therefore the computational cost. There are
different methods, and some of them will be more adequate than
other depending on the problem structure, number of variables,
etc. In this paper, the “Level”, “Top-down-Left-Right”, “AND”,
“Depth First Search” and “Breadth-First Search” methods have been
considered for listing the events, or vertices Ai, and a comparative
analysis has been performed in order to set the best ranking order.
The number of C-Ss is reduced according to the ranking of the
events, with the probability of the top event being the same in any
case. A suitable ranking will reduce the complexity of the calculation
of the top event probability. In order to set a correct ranking of
the events, the methods presented in Section 2.3 have been
considered.
Fig. 1.