An Overview of Multidimensional Data Models for OLAP

Multidimensional database technology is becoming more and more important in conjunction with data warehouses and OLAP analysis. What is still lacking is a commonly accepted formal foundation which can serve as a basis for future research and standardization. Recently, a multitude of interesting proposals on this topic have been published. OLAP applications have some special requirements that do not apply to other areas of multidimensional analysis (e.g. GIS, PACS). In this report, we list requirements that a formal model and a corresponding query language must fulfill to be suitable for OLAP. We present several recently proposed approaches that come closest to our requirements. For each approach, we give a brief description and a discussion of its suitability as a formal foundation for OLAP, with respect to our requirements. We conclude the report by giving some directions for future work in this area.