1. A method for converting decision flowcharts into decision probabilistic graphs on a data processing system comprising steps of: receiving a representation of a decision flowchart having evidence nodes, a root evidence node, and outcome nodes, where the outcome nodes are related to the evidence nodes by conclusion links; generating a probabilistic graph based on the decision flowchart, including: an aggregate outcome node having a plurality of outcome states, with each outcome state representing an outcome node of the decision flowchart; a plurality of test nodes with each of the test nodes matching an evidence node in the decision flowchart, and each test state matching a conclusion link from the evidence node in the flowchart; causal links between the aggregate outcome node and the evidence nodes; calculating a set of prior probabilities for the outcome states; and determining conditional probabilities for all test states by examining dependencies of conclusion links on the outcome nodes in the decision flowchart.