can you please clarify the difference between compatible and incompatible objects? when we will use these two?

Hai.

when ever we go for define the heirachy,,that time we go for this Incompatible objects..this one test thrugh Aggregate Navigator option..

When you are defining Aggregate tables in Universe design, you need to create hirarchies for aggregated objects, for that you need to make the relative objects incompatible (the objects which are of lower level of aggregation -- not of hirarchy).

If you have Year,Quarter,Month,Day as a hirarchy, while aggregation, you need to define as follows -

Year - Quarter,Month,Day Compatibles

Quarter - Month, Day Compatibles, Year Non-compatible

Month - Day Compatible, Year,Quarter Non-compatible

Cheers,

Patrick.