Simultaneous Determination of View Selection and Update Policy with Stochastic Query and Response Time Constraints
| Autor: | Chieh-Huan Ku, 古傑煥 |
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| Rok vydání: | 2004 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 92 Data warehouse is built up to reply queries efficiently. The view selection is to select a set of views to materialize under constraints, when minimizing the total of query processing cost and view maintenance cost. The update policy decides when to refresh the data in a data warehouse. Previous researches dealt with these two problems independently, however under the real situation, they are correlated with each other. Therefore, we simultaneously determine view selection and update policy in designing a data warehouse when the arrival of query follows a Poisson process and the response time of query is within a given threshold with a desired probability. In this research, we propose a mathematical model for determining optimal update policy when the set of materialized views are known. In the model, we adopt view maintenance policy for view update frequency, which does not change with the selected views in the former researches. Our model also incorporates the stochastic phenomenon to reflect the uncertain demand of query which is common in the real life. The mean system response time constrained by a specified time is formulated by a M/G/1 model. Furthermore, we develop a two-phase greedy algorithm for searching a better set of views to materialize. As to application, we consider different special cases to implement the mathematical model and the greedy algorithm. A computational analysis is conducted to explore the impact of different constraints and system parameters on view selection. In addition, we also design some experiments to evaluate the difference of view selection and solution running time between the greedy algorithm and exhaustive algorithm. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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