An approach to data management that allows an application to retrieve and manipulate data without requiring technical details about the data, such as how it is formatted at source, or where it is physically located, and can provide a single customer view (or single view of any other entity) of the overall data.
Unlike the traditional extract, transform, load ("ETL") process, the data remains in place, and real-time access is given to the source system for the data. This reduces the risk of data errors, of the workload moving data around that may never be used, and it does not attempt to impose a single data model on the data (an example of heterogeneous data is a federated database system). The technology also supports the writing of transaction data updates back to the source systems.
สรุปว่าต่างจาก Data warehouse ทีไม่ต้อง replicate ข้อมูลมารวมใน DW (i.e. ทำแค่ E&T ไม่ทำ L) และยังสามารถ write back to original DBs ได้ด้วย คล้ายๆกับแนวคิดของ Oracle VIEW
