Constructing an OLAP cube from distributed XML data

Abstract

On-Line Analytical Processing (OLAP) is a powerful method for analysing large data warehouse data. Typically, the data for an OLAP database is collected from a set of data repositories such as e.g. operational databases. This data set is often huge, and it may not be known in advance what data is required and when to perform the desired data analysis tasks. Sometimes it may happen that some parts of the data are only needed occasionally. Therefore, keeping the OLAP database constantly up-to-date is not only a highly demanding task but it also may be overkill in practice. This suggests that in some applications it would be more feasible to form the OLAP cubes only when they are actually needed. We present such a system. As the data sources may well be heterogeneous, we propose an XML language for data collection. Our system also has a facility, where the user may pose a query against a "universal" OLAP cube using the MDX language. The query is analysed to determine which data is required for the desired OLAP cube.