Methods and systems are described for simplifying a causal influence model that describes influence of parent nodes Xi (i=1, . . . , n) on possible states of the child node Y. The child node Y and each one of the parent nodes Xi (i=1, . . . , n) are assumed to be either a discrete Boolean node having states true and false, a discrete Ordinal node having a plurality of ordered states; and a Categorical node having a plurality of unordered states. The influence of each parent node Xi on the child node Y is assumed to be a promoting influence and an inhibiting influence. User interfaces are described that incorporate these specific node types.