An integer linear programming model with logical constraints for mail sorting facility selection

This paper studies a facility selection problem which is generalised from the design of a mail sorting system with multiple input and output. The problem is formulated as a 0–1 integer linear programming (ILP) problem with logical constraints. We show how the logical constraints can be embedded into an ILP model. We compare three strategies for handling local relations: (1) explicitly as added linear constraints; (2) implicitly as symbolic constraints; and (3) a combination of the two. The effectiveness of computations under different strategies is shown.