r:extendedDataTable allows selectionMode="none|single|multi" and it works prefectly, but UIExtendedDataTable does not have attribute selectionMode (getter and setter) currently.
Add property selectionMode for UIExtendedDataTable. Consider Enum as type. There is a class org.richfaces.model.SelectionMode and its is used in ExtendedDataTableRenderer .
We use direct component manipulation and type safe gettter and setter are better than the component.getAttributes() Map.