Graphvizでアクティビティ図(残骸)

Graphvizでアクティビティ図を書く。どうしても綺麗に書けない

図 Graphvizでアクティビティ図(残骸)

digraph sample {
  graph [fontname = "monospace", fontsize = 10];
  node  [fontname = "monospace", fontsize = 10];
  edge  [fontname = "monospace", fontsize = 10];

  // node
  node  [shape = circle];
  start [height = 0.3, width = 0.3, style = filled, fillcolor = black, label = ""];
  end   [height = 0.3, width = 0.3, style = filled, fillcolor = black, label = "", peripheries = 2];

  node [shape = diamond];
  branch;
  merge;

  node [shape = box];
  folk [height = 0.01, style = filled, fillcolor = black, label = ""];
  join [height = 0.01, style = filled, fillcolor = black, label = ""];

  node    [shape = ellipse];
  process [label = "処理"];
  object  [label = "<<Object>>\nオブジェクト"];

  // edge
  edge [style = solid, arrowhead = vee];
  start   -> branch;
  branch  -> folk;
  branch  -> merge;
  folk    -> process;
  process -> join;
  join    -> merge;
  merge   -> end;

  edge [style = dashed, arrowhead = vee];
  folk   -> object;
  object -> join;
}