How to Draw a Series-Parallel Digraph

Upward and dominance drawings of acyclic digraphs find important applications in the display of hierarchical structures such as PERT diagrams, subroutine-call charts, and is-a relationships. The combinatorial model underlying such hierarchical structures is often a series-parallel digraph. In this paper the problem of constructing upward and dominance drawings of series-parallel digraphs is investigated. We show that the area requirement of upward and dominance drawings of series-parallel digraphs crucially depends on the choice of planar embedding. Also, we present efficient sequential and parallel algorithms for drawing series-parallel digraphs. Our results show that while series-parallel digraphs have a rather simple and well understood combinatorial structure, naive drawing strategies lead to drawings with exponential area, and clever algorithms are needed to achieve optimal area.