Fig. 8.3.2 shows the classical ETL interface.

Fig. 8.3.2 ETL performs the transformation.

The transformation of data in this interface is from application data to corporate data.
The operational data are defined by each application. As a consequence, there are
inconsistent definitions of data, inconsistent formulas, inconsistent structures of data, and
so forth. But when the data pass through the ETL layer, the inconsistencies are resolved.

The ODS and the ETL Interface

There are however several variations to the classical ETL interface between the
operational environment and the data warehouse environment. One of those variations is
the inclusion of the ODS into the interface.

Fig. 8.3.3 shows that the ODS can participate in the interface.

Chapter 8.3: The Data Warehouse/Operational Environment Interface