1. A computer implemented method comprising: transforming a decision tree into an optimal compact representation, the decision tree having a plurality of variables, a root node, intermediate nodes, and leaf nodes, the decision tree being a leveled, read-once decision tree; and displaying the optimal compact representation of the decision tree; wherein the transforming comprises: converting the leveled, read-once decision tree into a collection of independent decision chains, each of the independent decision chains having one level for each variable and wherein the variables are arranged in the same order, thereby creating a decision chain set structure; computing an ordering of variables in the decision chain set structure to result in a directed acyclic graph with a minimum number of nodes; and converting the directed acyclic graph into an exception-based directed acyclic graph with a single exception to result in the optimal compact representation.