digraph Architecture {
   rankdir=TB;
   node [shape="box"];
   edge [arrowhead="open"];

   {rank=same; Guardian UserData;}

   subgraph clusterOutputs {
      label="Output files"
      style="filled";
      color="lightgrey";

      oSummary    [label="summary.xml"   color="cadetblue2" style="filled"];
      oAll        [label="all.xml"       color="cadetblue2" style="filled"];
      oDistance   [label="distance.xml"  color="cadetblue2" style="filled"];
      oOneperday  [label="oneperday.xml" color="cadetblue2" style="filled"];
      oChart      [label="chart.png"     color="cadetblue2" style="filled"];
      oCSV        [label="daily.csv"     color="cadetblue2" style="filled"];
      oOzi        [label="ozi.wpt"       color="cadetblue2" style="filled"];
   }

   subgraph clusterWebPage {
      label="Web Page(s)"
      style="filled";
      color="lightgrey";

      wpText    [label="text"];
      wpMap     [label="Google Map"];
      wpImage   [label="image"];
   }


   Guardian    [label="Guardian Mobility\nTracer data"];
   UserData    [label="User-defined\nCSV data"];
   Tracer      [label="Perl module\nGPS::Tracer" color="orange" style="filled"];
   jsSummary   [label="JavaScript\nsummary.js"   color="orange" style="filled"];
   jsTracer    [label="JavaScript\ntracer.js"    color="orange" style="filled"];
   download    [label="for download"];

   Guardian -> Tracer;
   UserData -> Tracer;
   Tracer -> oSummary -> jsSummary -> wpText;
   Tracer -> oAll -> jsTracer;
   Tracer -> oDistance -> jsTracer;
   Tracer -> oOneperday -> jsTracer;
   Tracer -> oChart -> wpImage;
   Tracer -> oCSV -> download;
   Tracer -> oOzi -> download;
   jsTracer -> wpMap;
}
