digraph G {
  // Durations (mean, variance). Use attrs: mean, var
  A [mean=2, var=0.2]; 
  B [mean=4, var=1.4];
  C [mean=3, var=0.3];
  D [mean=1, var=0.1];
  T [mean=0, var=0.0, shape=doublecircle];

  A -> B; A -> C; B -> D; C -> D; D -> T;
}