ryepup/c4-lab

digraph g {
  compound=true
  node[fontsize=12]
  edge[fontsize=12]

  g0 [shape="box" label=<
<b>system</b>
  >]
  g1 [shape="egg" label=<
<b>user</b>
  >]

  g1 -> g0 [label="talks to" dir="back"]
}