Top-Down Approach

This method begins with developing a comprehensive enterprise data warehouse (EDW) consolidating all organizational data. This central warehouse creates data marts to serve specific business units or functions. The top-down approach ensures a unified, consistent data model across the enterprise but typically requires more upfront investment in time and resources.

External Sources (ETL) >> Data Warehouse >> Data Mining
                                         >> Data Mart 1
                                         >> Data Mart 2

In the words of Inmon

"Data Warehouse as a central repository for the complete organization and data marts are created from it after the complete data warehouse has been created."