  Compound graphs are networks in which vertices can be grouped into larger
subsets, with these subsets capable of further grouping, resulting in a nesting
that can be many levels deep. In several applications, including biological
workflows, chemical equations, and computational data flow analysis, these
graphs often exhibit a tree-like nesting structure, where sibling clusters are
disjoint. Common compound graph layouts prioritize the lowest level of the
grouping, down to the individual ungrouped vertices, which can make the higher
level grouped structures more difficult to discern, especially in deeply nested
networks. Leveraging the additional structure of the tree-like nesting, we
contribute an overview+detail layout for this class of compound graphs that
preserves the saliency of the higher level network structure when groups are
expanded to show internal nested structure. Our layout draws inner structures
adjacent to their parents, using a modified tree layout to place substructures.
We describe our algorithm and then present case studies demonstrating the
layout's utility to a domain expert working on data flow analysis. Finally, we
discuss network parameters and analysis situations in which our layout is well
suited.
