Hierarchies in a multidimensional model: From conceptual modeling to logical representation

Hierarchies are used in data warehouses (DWs) and on-line analytical processing (OLAP) systems to see data at different levels of detail. However, many kinds of hierarchies arising in real-world situations are not addressed by current OLAP systems. Further, there is still no agreement on a conceptual model for DW and OLAP design that offers both a graphical representation and a formal definition.In this paper, we formally define the MultiDimER model, a conceptual multidimensional model that allows to represent facts with measures as well as the different kinds of hierarchies already classified in our previous work [E. Malinowski, E. Zimányi, OLAP hierarchies: a conceptual perspective, in: Proceedings of the 16th International Conference on Advanced Information Systems Engineering, 2004, pp. 477–491]. We also present the mapping of such hierarchies to the relational model, as well as their implementation in commercial DW products.