The Block Layout can be used to create a layout for a process graph. For this, it uses well-known Petri-net-based reduction rules to reduce the entire net into a single place. For nicely structured process graphs, this layout works quite well, but for more complex structured graphs, the resulting layout needs to be improved. Either good heuristics are needed for deciding (n case we have a choice) which way to go, or new reduction rules that can cope with more complex structured graphs.
For more information, contact Eric Verbeek.