Christian Koncilia

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" The Times They Are A-Changing " (B. Dylan), and with them the structures, schemas, master data, etc. of data warehouses. For the correct treatment of such changes in OLAP queries the orthogonal-ity assumption of star schemas has to be abandoned. We propose the COMET model which allows to represent not only changes of transaction data, as usual in data(More)
A data warehouse (DW) provides an information for analytical processing, decision making, and data mining tools. On the one hand, the structure and content of a data warehouse reflects a real world, i.e. data stored in a DW come from real production systems. On the other hand, a DW and its tools may be used for predicting trends and simulating a virtual(More)
Data Warehouses provide sophisticated tools for analyzing complex data online, in particular by aggregating data along dimensions spanned by master data. Changes to these master data are a frequent threat to the correctness of OLAP results, in particular for multi-period data analysis, trend calculations, etc. As dimension data might change in underlying(More)
In a typical BI infrastructure, data, extracted from operational data sources, is transformed, cleansed, and loaded into a data warehouse by a periodic ETL process, typically executed on a nightly basis, i.e., a full day's worth of data is processed and loaded during off-hours. However, it is desirable to have fresher data for business insights at near(More)
Changes in transaction data are recorded in data warehouses and sophisticated tools allow to analyze these data along time and other dimensions. But changes in master data and in structures, surprisingly, cannot be represented in current data warehouse systems impeding their use in dynamic areas and/or leading to erroneous query results. We propose a(More)
We present a technique for discovering and representing changes between versions of data warehouse structures. We select a tree comparison algorithm, adapt it for the particularities of multidimensional data structures and extend it with a module for detection of node re-namings. The result of these algorithms are so called edit scripts consisting of(More)