fireObserver(new SetEvent(this, propertyName, previous, value));
fireObserver(new SetEvent(this, propertyName, previous, value), false);
    public void set(String propertyName, Object value) {        validate(true);        // if value is an object or scalar then it adds to data container        Property prop = checkProperty(propertyName);        if (prop.isCollection()) {            throw new PersistenceException(                "Cannot set a multi valued property."                );        }        // make sure that the property is loaded so it can be nulled correctly        // also necessary for observer firing.        Object previous = get(propertyName);        m_data.set(propertyName, value);        fireObserver(new SetEvent(this, propertyName, previous, value));    }