digraph G {
    compound=true;
    rankdir=LR;

    subgraph cluster0 {
        label = "Network";
	{rank=source; client; server;}
	client;
	server;	
	color = black;
    }

    subgraph cluster1 {
        label = "Game Engine";
	{rank=min; gs; physics; interpolation; }
	gs;
	physics;
	interpolation;
	color = black;
    }

    {rank=sink; input; graphics;}
    client->server;
    server->client;

    gs->physics;	
    physics->interpolation;

    input->interpolation;
    input->client;
    interpolation->graphics;

    server->gs;
    gs->client;
}