return getSelectorNames(and.getConstraint1(), and.getConstraint2());
} else if (constraint instanceof Or) {
Or or = (Or) constraint;
return getSelectorNames(or.getConstraint1(), or.getConstraint2());
} else if (constraint instanceof Not) {
Not not = (Not) constraint;
return getSelectorNames(not.getConstraint());
} else if (constraint instanceof PropertyExistence) {
PropertyExistence pe = (PropertyExistence) constraint;
return Collections.singleton(pe.getSelectorName());
} else if (constraint instanceof Comparison) {
Comparison c = (Comparison) constraint;