digraph G {

	subgraph cluster_0 {
		style=filled;
		color=lightgrey;
		node [style=filled,color=white];
		a0 -> a1;
		a1 -> a2;
		a2 -> a3;
		label = "process #1";
	}

	subgraph cluster_1 {
		node [style=filled];
		b0 -> b1;
		b1 -> b2;
		b2 -> b3;
		label = "process #2";
		color=blue;
	}
	start -> a0;
	start -> b0;
	a1 -> b3;
	b2 -> a3;
	a3 -> a0;
	a3 -> end;
	b3 -> end;

	start [shape=Mdiamond];
	end [shape=Msquare];
}