Binary Decision Diagrams and Its Variable Ordering for Disjoint Network

We know that binary decision diagram is a data structure that is used to store a Boolean function. They are used to find out the terminal reliability of a computer communication network. To generate the binary decision diagram of a given computer communication network, we need to order the edges of the given computer communication network because the size of the binary decision diagram is dependent on the ordering of the variables (edges). There are three types of variable ordering; optimal, good and bad ordering. Optimal ordering are those ordering which generate minimum size binary decision diagram. In this paper we have shown that if a directed computer communication network has m disjoints min-paths then m! optimal variable orderings exist to generate the binary decision diagrams of the given computer communication network.