digraph {
	rankdir="LR";
	subgraph {
		rank="same";
		1 [ label="callP", color="green" ]
		2 [ label="doneP", color="red" ]
	} subgraph {
		rank="same";
		3 [ label="callQ", color="green" ]
		4 [ label="doneQ", color="red" ]
	} subgraph {
		rank="same";
		5 [ label="call", color="red" ]
		6 [ label="done", color="green" ]
	}

	5 -> 1
	5 -> 3
	2 -> 6
	4 -> 6
	1 -> 2
	3 -> 4
	5 -> 6
}