Applying GRID Technologies to XML Based OLAP Cube Construction

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, storing all data to the OLAP database and keeping this 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. However, the OLAP cube construction can be a slow process. Thus, we present a system that applies Grid technologies to distribute the computation. As the data sources may well be heterogeneous, we propose an XML language for data collection. The user's definition for a OLAP new cube often includes selecting and aggregating the data. In our system this computation is distributed to the computers that store the original data. This reduces the network traffic and speeds up the computation that is now performed in parallel. The sub results are sent back to the 'collecting server'. Usually, the results do not arrive simultaneously. However, the collecting server starts to process a sub result immediately after it has arrived. Therefore, there is no need to wait that all sub result are received. We have implemented a prototype for the system. The implementation applies Spitfire software and Mobile Analyzer technology. They both are Grid based products applying Grid Security Infrastructure.