In one embodiment, a computing system identifies one or more terminal nodes in a digraph, and then back-walks primitives up the digraph from each terminal node to a corresponding parent terminal node or a root of the digraph, whichever is first. The system then identifies chains of back-walked primitives for each of the one or more terminal nodes (e.g., where each chain consists of a respective terminal node and any primitives either a) up to but not including a corresponding parent terminal node or else b) up to and including the root of the digraph when the back-walking reaches the root). Based on this, the system can then merge each set of any two or more chains of the identified chains that intersect on a decision operation into a corresponding new single chain, and maps each of the chains to a respective rule.