The IEventListener interface is declared as following:

 public interface IEventListener {
     void eventRaised(Event ev, Object sender, EventArgs args);
 }

For specific events, such as PropertyChangedEvent triggered by following code within a model class:

 getPropertyChangedEvent().raise(this, e);

where "e" is PropertyChangedEventArgs, client code will have to do unnecessary typecast like this:

 ...
 public void eventRaised(Event ev, Object sender, EventArgs args) {
     PropertyChangedEventArgs actualArgs = (PropertyChangedEventArgs) args;
 }
 ...

To eliminate unnecessary typecasts as shown above, the IEventListener interface should be improved (i.e. parametrized).