Updating allows the data sources to notify clients that a different dataset will be returned if they call getDataSet again. Implementations should take into account that excessive update notifications may be ignored. Updates should be made by calling the registered listeners' propertyChange method, with an appropriate PropertyChangeEvent: listener.propertyChange( new PropertyChangeEvent( this, Updating.PROP_DATASET, null, null ) ) to force the client to post a new request, or new PropertyChangeEvent( this, "dataSet", null, ds ) if the dataset is trivially available. Developers should consider using java.beans.PropertyChangeSupport to implement this capability, so that it's firePropertyChange method can be used.