Hierarchies and planarity theory
Giuseppe Di Battista, Enrico Nardelli · IEEE Transactions on Systems Man and Cybernetics · 1988
In diagrammatic representations of hierarchies the minimization of the number of crossings between edges is a well-known criterion for improving readability. An efficient algorithm for testing if a hierarchy is planar (i.e. if it can be drawn without edge crossings) is proposed. A complete combinatorial characterization of the class of planar hierarchies is also given.>