On the 2-Layer Window Width Minimization Problem

When interacting with a visualization of a bipartite graph, one of the most common tasks requires identifying the neighbors of a given vertex. In interactive visualizations, selecting a vertex of interest usually highlights the edges to its neighbors while hiding/shading the rest of the graph. If the graph is large, the highlighted subgraph may not fit in the display window. This motivates a natural optimization task: find an arrangement of the vertices along two layers that reduces the size of the window needed to see a selected vertex and all its neighbors. We consider two variants of the problem; for one we present an efficient algorithm, while for the other we show NP-hardness and give a 2-approximation.