In this demo, the starting point is a model diagram which has already been laid out by hand. This provides a nice comparsion of how well (or how badly...) the automatically-laid-out diagram is compared to the human one.
However, the main point in having a mechanism for doing this is to enable text-equation models (for example, those obtained by listing out the equations in a Stella, Vensim or Simile model) to be loaded into Systo and rendered as a diagram. This requires a little more work - the widget has to work out the nodes (variables) and arcs (influence or flow arrows) from the equations - but that's not too difficult.
To see the demo work, simply click on the Layout button. Wait until you get a message saying that the layout process is complete, then you can click the button again to see a different layout.