Data Warehousing is the function responsible for identifying, collecting, refining, integrating, and controlling heterogeneous data from internal and external sources to enable access by knowledge workers for analysis and reporting. The data in the warehouse is organized by subject area (Customers, Products, Finance, HR) to facilitate a higher-level (enterprise) view of the data. Data may also be aggregated, summarized, and migrated to data marts for a narrower business focus.