digraph g {
    subgraph {
		l1; l2; l3; l4; l5;
		"x_in = a"; "y_in = b"; "a = x_out";
	}
	subgraph {
		l8; l9; l10; l12;
		"x = x_in"; "y = y_in"; "x_out = x";
	}
	l1 [label="main()"];
	l2 [label="a = 10"];
	l3 [label="b = 20"];
	l4 [label="f(a, b)"];
	l5 [label="print(a)"];
	l8 [label="f()"];
	l9 [label="while (x > y)"];
	l10 [label="x = x + 1"];
	l12 [label="print(x)"];
	// Rank
	{ rank = same; l9; l12; }
	// s0 -> s2 [style=invis];
	// Control
	{
		edge [style = bold];
		l1 -> {l2 l3 l4 l5};
		l4 -> {"x_in = a" "y_in = b" "a = x_out"};
		l8 -> {"x = x_in" "y = y_in" l9 l12 "x_out = x"};
		l9 -> l10;
	}
	// Data
	{
		edge [color = red];
		edge [constraint = false];
		l2 -> "x_in = a";
		l3 -> "y_in = b";
		"a = x_out" -> l5;
		{"x = x_in" l10} -> {l9 l10 l12 "x_out = x"};
		"y = y_in" -> l9;
	}
	{
		edge [style=dashed];
		edge [constraint=false];
		"x_in = a" -> "x = x_in";
		"y_in = b" -> "y = y_in";
		l4 -> l8 [constraint=true];
		"x_out = x" -> "a = x_out";
	}
    {edge [color=blue,constraint=false]; {"x_in = a" "y_in = b"} -> "a = x_out"}
    {edge [style=invis]; "y_in = b" -> l8; "y = y_in" -> l9; }
}