Mondrian Olap drilldown algorithm

Question

I didn't found but may be someone could me explain - OLAP cube is a combination of all possible aggregation, so related to Mondrian - leaf level is data in fact table or it is a minimum aggregate (cell) ? Thanks.

Answer 1

Level are attributes (characteristics of the cells aggregated measures) of dimension tables. Each dimension table is a dimension in the data cube. So to perform an OLAP operation drill-down, you should increase the granularity of the view. While the roll-up the reverse.

Assuming you have a consumer dimension. In this dimension you have the following attributes: region, country and city. A drill-down operation is view a nation and you then view the cities of this nation. How does the Mondrian, for example. The roll-up operation is the reverse, as you view the nations, you do a roll-up and see the parents of that nation. That is, the drill-down do levels down the hierarchy, while the roll-up rises.

These data are seen always in accordance with an aggregate measure, which in this case could be a recipe for profit. So you could see the recipe for the nation, and then navigate the hierarchy of cities and seeing the country, making a drill-down and roll up.

Access BJIn OLAP. It performs these OLAP operations and contains examples of them.1

I hope this helps.