Journal article
An aggregation algorithm using a multidimensional file in multidimensional OLAP
Information sciences, v 152, pp 121-138
01 Jun 2003
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
Aggregation is an operation that plays a key role in multidimensional OLAP (MOLAP). Existing aggregation methods in MOLAP have been proposed for file structures such as multidimensional arrays. These file structures are suitable for data with uniform distributions, but do not work well with skewed distributions. In this paper, we consider an aggregation method that uses dynamic multidimensional files adapting to skewed distributions. In these multidimensional files, the sizes of page regions vary according to the data density in these regions, and the pages that belong to a larger region are accessed multiple times while computing aggregations. To solve this problem, we first present an aggregation computation model that uses the new notions of
disjoint-inclusive partition and
induced space filling curves. Based on this model, we then present a dynamic aggregation algorithm. Using these notions, the algorithm allows us to maximize the effectiveness of the buffer––we control the page access order in such a way that a page being accessed can reside in the buffer until the next access. We have conducted experiments to show the effectiveness of our approach. Experimental results for a real data set show that the algorithm reduces the number of disk accesses by up to 5.09 times compared with a naive algorithm. The results further show that the algorithm achieves a near optimal performance (i.e., normalized I/O=1.01) with the total main memory (needed for the buffer and the result table) less than 1.0% of the database size. We believe our work also provides an excellent formal basis for investigating further issues in computing aggregations in MOLAP.
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Details
- Title
- An aggregation algorithm using a multidimensional file in multidimensional OLAP
- Creators
- Young-Koo Lee - Korea Advanced Institute of Science and TechnologyKyu-Young Whang - Korea Advanced Institute of Science and TechnologyYang-Sae Moon - Wrexham UniversityIl-Yeol Song - College of Information Science and Technology, Drexel University, Philadelphia, PA 19104, USA
- Publication Details
- Information sciences, v 152, pp 121-138
- Publisher
- Elsevier
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Information Science
- Web of Science ID
- WOS:000182691600006
- Scopus ID
- 2-s2.0-0038636388
- Other Identifier
- 991021806419004721
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- Collaboration types
- Domestic collaboration
- International collaboration
- Web of Science research areas
- Computer Science, Information Systems