if (ans.satisfiable()) {
// You can query "ans" to find out the values of each set or type.
// This can be useful for debugging.
//
// You can also write the outcome to an XML file
ans.writeXML("alloy_example_output.xml");
//
// You can then visualize the XML file by calling this:
if (viz==null) {
viz = new VizGUI(false, "alloy_example_output.xml", null);
} else {