digraph sampleo {
  blogger1         [label="Blogger"];
  blogger_pro_beta [label="Blogger Pro beta"];
  blogger_pro      [label="Blogger Pro"];
  blogger2         [label="Blogger v1"];
  blogger_beta     [label="Blogger beta"];
  blogger3         [label="Blogger v2"];
  blogger_in_draft [label="Blogger in draft"];

  blogger_fin1     [style=filled, fillcolor="gray", label="Blogger"];
  blogger_fin2     [style=filled, fillcolor="gray", label="Blogger v1"];
  now1             [shape=none, label="現在"];
  now2             [shape=none, label="現在"];

  "1999.8" -> "2000.11" -> "2002.1" -> "2003.2" -> "2006.8" -> "2006.12" -> "2007.6";
  {rank=same; "1999.8"; blogger1;}
  {rank=same; "2000.11"; blogger_pro_beta;}
  {rank=same; "2002.1"; blogger_pro}
  {rank=same; "2003.2"; blogger_fin1; blogger2}
  {rank=same; "2006.8"; blogger_beta}
  {rank=same; "2006.12"; blogger_fin2; blogger3}
  {rank=same; "2007.6"; blogger_in_draft}
  {rank=same; now1; now2}

  pyra    [shape=none, label="Pyra Labs"];
  pro     [shape=none, label="有償版"];
  google1 [shape=none, label="Google v1"];
  google2 [shape=none, label="Google v2"];
  google3 [shape=none, label="開発版"];
  {rank=same;
     pyra; pro; google1; google2; google3; }
  pyra -> pro -> google1 -> google2 -> google3 [style=invis];

  {
    edge [style=invis];
    pyra -> blogger1;
    pro -> blogger_pro_beta;
    google1 -> blogger2;
    google2 -> blogger_beta;
    google3 -> blogger_in_draft;
  }

  blogger1 -> blogger_fin1; 
  blogger_pro_beta -> blogger_pro;
  blogger_fin1 -> blogger2 [label="Google による買収"];
  blogger2 -> blogger_fin2 -> blogger3 -> now1;

  blogger_beta -> blogger3;
  blogger_in_draft -> now2;
}