[graphviz]

The Graphviz project often wished to find a convincing formal definition of what it means for curves (spline sequences) that connect two points and are routed around obstacles to be "natural". Maybe machine learning will help with this before long. Something similar could be said for other geometric properties of diagrams. Many aesthetics have been proposed and studied, but do we know what blend is preferred by human subjects? How much do individuals vary in this?