A real-time system receives a selection structure formed by weighted rules joined by links, each of the weighted rules including a condition part, a conclusion part and a weight. The selection structure is an Algebraic Decision Diagram (ADD) that includes internal nodes, each representing a decision point and terminal nodes, each representing a subset of candidate results having an accumulated weight. In response to a query that specifies a set of conditions, the ADD is traversed by making a series of decisions at decision points of the ADD to reach at least one terminal node having a maximum accumulated weight among terminal nodes that satisfy the set of conditions. The subset of candidate results represented by the at least one terminal node is selected as the output for responding to the query.