INFORMATION SYSTEMS IN MANAGEMENT IV

sent them chronologically, i.e. bottom-up. In the lowest level of the Figure 1 thereexist operational databases that were designed and created for various applications.These databases are usually internal in an enterprise but the data may be also importedfrom outside or even from usual text files. Various data schemes may beused for storing this information. Data of a consecutive layer are obtained from thedata of the lower layer.Figure 1. Architecture of a data warehouse.Source: Own preparation based on [7].Proper parts of data warehouse are situated in the middle and upper layers ofthe Figure 1. Basic data warehouse, called global or corporational, is in the middlelayer and contains results of processing of data coming from the lowest layer.Together with an information its history is stored here. After each update a datawarehouse is completed by new properly processed information coming from anoperational database of the lowest layer. Indeed, creation of a data warehousemight remind an adding of consecutive materialized relational views over somedatabases.47