Abstract: A method comprises obtaining data from a source system. Further, the obtained data is pre-processed by a stepwise operation to generate pre-processed data. The last operated upon data is recorded. In addition, the pre-processed data is transformed into subject-oriented data by utilizing reusable primary keys and Relational Database Management System dates in the source system to link related pre-processed data. Additionally, the subject-oriented data is stored in a data warehouse. The Relational Database Management System dates are utilized for distinctly characterizing the subject-oriented data when a plurality of tables containing data with duplicate primary keys are combined in the data warehouse.