Please see the paper here:
The visualisations produced in this way are very powerful for showing the flow of material from one point to another. I can't seem to get this sort of effect right in yEd, however, because:
Hierarchical layout, using the diagram as a sketch and using the "From Sketch" Layer Assignment Policy manages to keep nodes in roughly the same positions, but there seems to be no way of preserving the relative x and y co-ordinate ranks of each node - they snap to grid, meaning that the ordering information is lost, since both nodes now have the same ordinate value.
Edge width is not data dependent. It is essential that there be some way to set the width of an edge, so that the size of the flow is indicated to the reader.
Hidden Intermediate Nodes for edge merging and splitting are required.
I think it would be incredibly cool if I could create flow Maps in yEd.