Dimensional models are built by business process area, e.g. store sales, inventory, claims, etc.
The same modeling approach, at the logical level, can be used for any physical form, such as multidimensional database or even flat files.
The basics in the design build on the actual business process which the data warehouse should cover.
This could for instance be “An individual line item on a customer slip from a retail store”.
You might find it necessary to go back to this step to alter the grain due to new information gained on what your model is supposed to be able to deliver.
After defining the dimensions, the next step in the process is to make keys for the fact table.
Therefore, most of the fact table rows are numerical, additive figures such as quantity or cost per unit, etc.
However, some features of Hadoop require us to slightly adapt the standard approach to dimensional modelling.