16. In a computer system having a processor and a storage device connected to the processor, wherein the storage device stores computer executable instructions and a data structure, the data structure storing a belief network, the belief network probabilistically relating a plurality of different input variables to a plurality of different output decisions, a method for use in the system for improving accuracy of the belief network, belief network having nodes and arcs indicating relationships between the nodes, each node having a decision graph containing probabilities for rendering inferences, comprising the steps, implemented by the processor through execution of the instructions, of: scoring one of the decision graphs in one of the nodes of the belief network to determine goodness at rendering inferences; and adjusting the scored decision graph to improve the score of the scored decision graph and to improve the accuracy of the belief network such that the adjustment creates a plurality of paths in the scored decision graph that refer to a common probability such that given one of the input variables, as an observation, probabilistic inference undertaken by the system and based on the stored belief network, will yield through enhanced accuracy, one of the output decisions.
22. The method of claim 16 wherein the adjusting step includes adjusting the decision graph to generate a plurality of candidate decision graphs, scoring the generated decision graphs, determining which among the generated decision graphs has a best score, and selecting the decision graph having the best score for use in the one node of the belief network.