Abstract

A level graph G -- (V, E, q) is a directed acyclic graph with a mapping q: V - {1, 2,...,k), k _ 1, that partitions the vertex set V as V-- V10V20 ...V k, vj = q-l(j), Vi [ vj = for i j, such that q(v) _ q(u) + 1 for each edge (u, v) E. The level planarity testing problem is to decide if G can be drawn in the plane such that for each level V i, all v V i are drawn on the line li -- {(x, k - i) ] x ), the edges are drawn monotonically with respect to the vertical direction, and no edges intersect except at their end vertices. In order to

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