  Bottom-up layout algorithms for compound graphs are suitable for presenting
the microscale view of models and are often used in model-driven engineering.
However, they have difficulties at the macroscale where maintaining the
overview of large models becomes challenging. We propose top-down layout, which
utilizes scale to hide low-level details at high zoom levels. The entire
high-level view can fit into the viewport and remain readable, while the
ability to zoom in to see the details is still maintained. Top-down layout is
an abstract high-level layout process that can be used in conjunction with
classic layout algorithms to produce visually compelling and readable diagrams
of large compound graphs.
