A Bayesian network is a graphical model where each of the nodes represent random variables. Each node is connected to other nodes by directed arcs. Each arc represents a conditional probability distribution of the parents given the children. The directed edges represent the influence of a parent on its children. The nodes usually represent some real-world objects and the arcs represent some physical or logical relationship between them. Bayesian networks are used in many applications like automatic speech recognition, document/image classification, medical diagnosis, and robotics.