private XStream xt;
private static final ScenarioXMLPersistence INSTANCE = new ScenarioXMLPersistence();
private ScenarioXMLPersistence() {
xt = new XStream(new DomDriver());
xt.alias("scenario", Scenario.class);
xt.alias("execution-trace", ExecutionTrace.class);
xt.alias("expectation", Expectation.class);
xt.alias("fact-data", FactData.class);
xt.alias("fact", Fact.class);