// save
modelManager.addModelElement(tl1);
modelManager.addModelElement(e1);
modelManager.addModelElement(e2);
modelManager.addModelElement(e3);
modelManager.addModelElement(e4);
PersistenceManager.getInstance().saveToFile(EWD_FILE);
// restore
modelManager.clearModel();
PersistenceManager.getInstance().loadFromFile(EWD_FILE);