A Systematic Approach to Multidimensional Databases

Multidimensional databases are large collections of data, often historical, used for sophisticated analysis oriented to decision making. This activity is supported by an emerging category of software technology, called On-Line Analytical Processing (OLAP). In spite of a lot of commercial tools already available, a fundamental study for OLAP systems is still lacking. In this paper we introduce a model and a query language to establish a theoretical basis for multi-dimensional data. The model is based on the notions of dimension and f-table. Dimensions are linguistic categories corresponding to di erent ways of looking at the information. F-tables are the constructs used to represent factual data, and are the logical counterpart of multi-dimensional arrays, the way in which current analytical tools store data. The query language is a calculus for f-tables, and as such it o ers a high-level support to multi-dimensional data analysis. Scalar and aggregate functions can be embedded in calculus expressions in a natural way. We compare our model and language with other approaches, and discuss on several issues related to multidimensional databases. Finally, we identify important research topics that need to be investigated in this context.