digraph G {
  graph [rankdir=LR, size="7,1.5"]
  subgraph cluster_0 {
    graph [label=User]
    edge [style=dashed]
    browser [label="WWW\nbrowser" URL="http://www.mozilla.org/"]
    svgplugin [label="SVG Plugin" URL="http://www.adobe.com/svg/viewer/install/old.html"]
    pdfplugin [label="PDF Plugin" URL="http://www.adobe.com/support/downloads/product.jsp?product=10&platform=unix"]
    svgplugin -> browser
    svgplugin -> browser [dir=back]
    pdfplugin -> browser
    pdfplugin -> browser [dir=back]
    {
      graph [rank=same]
      pngpage [label=PNG shape=box URL="/cgi-bin/webdot/webdot/demo.dot.dot.png"]
      svgpage [label=SVGZ shape=box URL="/cgi-bin/webdot/webdot/demo.dot.dot.svgz"]
      pdfpage [label=PDF shape=box URL="/cgi-bin/webdot/webdot/demo.dot.dot.pdf"]
    }
    pngpage -> browser [dir=none style=dotted]
    svgpage -> svgplugin [dir=none style=dotted]
    pdfpage -> pdfplugin [dir=none style=dotted]
  }
  subgraph cluster_1 {
    graph [label="Server 1"]
    httpd1 [label=httpd URL="http://httpd.apache.org/"]
    webdot [label="/cgi-bin/webdot" style=filled fillcolor=yellow color=black URL="/webdot/"]
  }
  subgraph cluster_2 {
    graph [label="Server 2"]
    httpd2 [label=httpd URL="http://httpd.apache.org/"]
    "demo.dot" [shape=box URL="/webdot/demo.dot"]
    httpd2 -> "demo.dot" [dir=none style=dotted]
  }
  browser -> httpd1 -> webdot -> httpd2
  browser -> httpd1 -> webdot -> httpd2 [dir=back]
}