Incremental update of aggregate information in the web-based data warehouse

Pao Yue-kong Library Electronic Theses Database

Incremental update of aggregate information in the web-based data warehouse


Author: Chan, Suk-fong Miranda
Title: Incremental update of aggregate information in the web-based data warehouse
Degree: M.Sc.
Year: 2000
Subject: Data warehousing
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Computing
Pages: v, 65 leaves : ill. ; 30 cm
Language: English
InnoPac Record:
Abstract: In the web computing environment of the future, a large number of users equipped with low power computers will query databases over the wired or wireless communication channels; Sending access-requests from the computer to the online database server may be expensive due to the limited uplink bandwidth in a mobile environment. In addition, this approach may incur inefficiency and delay in query processing, especially when queries are issued multiple times, when information sources are slow, expensive, or periodically unavailable. This is worse if a query is defined on multiple data sources. Data warehousing can alleviate these problems. In the data warehousing approach, information from each data source that may be of interest is extracted in advance, translated and filtered as appropriate; merged with relevant information from other sources, and stored in a repository which is called data warehouse. When a query is posed, the query is evaluated directly in the repository, without accessing the original information sources. In addition to base data, data warehouses also tend to contain highly aggregated and summarized information suitable for decision support. As changes are made to the data sources, the warehouse views must be updated to reflect the changed state of the data sources. It can be re-computed from scratch, or incremental maintenance techniques can be used to calculate the changes to the Views due to the source changes. In this dissertation, an incremental view maintenance method based on the net changes on base table is used to maintain the views efficiently in the presence of aggregation and summary information. An architecture of the web-based data warehousing system will be proposed to minimize the workload of the data warehouse. Moreover, the performance study comparing the algorithm to the existing maintenance algorithm will also be conducted. A prototype application utilizing the new maintenance algorithm is developed.

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