digraph hierarchy {
  nodesep=1.0 // increases the separation between nodes
             
  node [color=Red,fontname=Courier,shape=box] //All nodes will this shape and colour
  edge [color=Blue, style=dashed] //All the lines look like this

  Model->{Package1 Package2 System}
  Package1->{Class1 Class2}
  System->Subsystem
  {rank=same;Subsystem Class1 Class2}  // Put them on the same level
}