digraph G {

  rankdir=TB;
  ranksep = 1;
  nodesep = 2;
  node [shape = box, style = filled, color = black]
  graph [style = solid, fontcolor = black, labelloc = b]

  DC [fillcolor = darkseagreen, height = 1, label = "Dialog Client n Java"]
  SI [fillcolor = gray80, height = 1, label = "SL Interface n C++"]
  PDC [fillcolor = coral2, height = 1, label = "Physical Domain n Client n C++"]
  SLBD [fillcolor = cadetblue3, height = 1, label = "SL Block Diagram"]

  {rank = source; SLBD}
  {rank = same; DC; SI; PDC;}

  SLBD->SI [color = firebrick, fontsize = 10, fontcolor = firebrick, label = "1. CTRL-D n NetList"]
  SI->SLBD [color = firebrick, fontsize = 10, fontcolor = firebrick, label = "2. mdlProps = get_param(handle)", dir = both]
  SI->PDC [color = firebrick, fontsize = 10, fontcolor = firebrick, label = "3. mdl = PMModel(mdlProps)", dir = both, tailport = se, headport = sw]
  SI->PDC [color = firebrick, fontsize = 10, fontcolor = firebrick, label = "4. mdl->compile"]
  SI->SLBD [color = firebrick, fontsize = 10, fontcolor = firebrick, label = "7. setupSFcn(sFcnData) "]
  DC->PDC [color = firebrick, fontsize = 10, fontcolor = firebrick, label = "5. visualize(sceneData)", tailport sw, headport = se, dir = back]
  SI->SLBD [color = firebrick, fontsize = 10, fontcolor = firebrick, label = "6. setupSFcn(sFcnData) "]
    DC->SI
}