digraph Union {
  mindist = 2.0
  1 -> 2 [label="annotation"]
  1 -> 3 [label="simpleType"]
  2 -> 3 [label="simpleType"]
  3 -> 3 [label="simpleType"]
  1 [shape=doublecircle, style=filled, color=blue]
  2 [shape=doublecircle, style=filled, color=green]
  3 [shape=doublecircle, style=filled, color=green]
}