digraph G {
    compound=true;
    subgraph cluster1 {
        label="Legend";
        "Generated Files" [fillcolor=lightgray style=filled shape=ellipse];
        "Generated File"  [shape=ellipse];
        "Processing"      [shape=diamond fontsize=12];
        "Authored Files"  [fillcolor=lightgray style=filled shape=box];
        "Authored File"   [shape=box];
    }
}
