Data warehouse-Time variant The time horizon ha'raiz(n for the data warehouse is significantly longer than that of operational systems Operational database: current value data Data warehouse data: provide information from a historical perspective( e.g. past 5-10 years) Every key structure in the data warehouse Contains an element of time, explicitly or implicitly But the key of operational data may or may not contain time element7 Data Warehouse—Time Variant ◼ The time horizon [hə'raɪz(ə)n] for the data warehouse is significantly longer than that of operational systems ◼ Operational database: current value data ◼ Data warehouse data: provide information from a historical perspective (e.g., past 5-10 years) ◼ Every key structure in the data warehouse ◼ Contains an element of time, explicitly or implicitly ◼ But the key of operational data may or may not contain “time element