Behaviour Navigaton and Display attributes in Bex Reporting

In SAP BW Master data attributes are classified in to
Display attributes
Navigational attributes.
The attributes are further classified into 1. Time dependent attributes
                                                            2. Time Independent attributes.
Display attributes are used to provide additional descriptive information only there not maintained in the infocube dimensions. They doesn't support OLAP functions such as drill down, drill across, free characteritic, filters, variables etc......... and we cannot prepare aggregates using display attributes.
Navigational attributes are used to display additional descriptive function and they support all olap functions as basic characteristics.
Navigational attributes(their MD ids) are directly saved in Infocube Dimensions. A navigational attribute behaves like display attribute as well as a navigational attribute. It is possible to create aggregates using navigational attributes.