The Interactive Data Warehouse: Introducing Transactional Data Marts and "Smart Applications" to Interact With Data Warehouse Data

Traditional data warehouse literature describes four maturity levels for a data warehouse, the highest being the "Integrated data warehouse", where triggers in the operational systems keep the data warehouse immediately updated, and new transactions from the data warehouse are immediately written back to operational systems. But the number of different operational systems, the absence of proper legacy system API's, and the difference in transactional level between the data warehouse and operational systems make this unattainable for most enterprises.