Bayesian networks are graphical models of a problem domain using conditional probabilities to represent relationships between events – e.g. the probability of developing lung cancer given the fact that the patient is a smoker. Bayesian networks is a newer AI technology that enables one to reason in complex situations with many confusing, uncertain and conflicting sources of information. Bayesian networks are based on Bayes’ formula for reversing the causal direction of conditional probabilities, allowing one to reason about causes based on information about the effects or symptoms.