A Framework for Query Transformations in Deductive Databases

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概要

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• Several methods that transform queries to their equivalents in order to improve the performance of the bottom-up approach have been proposed for recursive query processing. This paper discusses the foundation of query transformations. First, the role of the query transformations is discussed and the concept of goal equivalent transformation is introduced. Goal equivalent transformation is transformation that preserves the answer to a query but allows the least model of the database to change. Because the least model of the database is computed by the bottom-up approach, the performance can be improved by changing the size of the least model. Next, ways to obtain smaller least models are discussed, and a conceptual procedure called clause replacement is proposed. Examples of procedures, which are applications of clause replacement using the fundamental prin-cip1es of first order logic such as resolution and subsumption, are shown. They include procedures called Horn clause transformation (HCT) by partial evaluation, HCT by substitution, and HCT by restrictor. It is shown that several transformation methods can be reformulated and generalized using clause replacement as a common foundation, because HCTs correspond to generalizations of methods such as the distribution of selections and the magic sets. Properties of HCTs are also compared, and it is shown that compositions of HCTs are more effective than single HCTs.

• 一般社団法人情報処理学会の論文
• 1990-03-15

著者

• Itoh Hidenori

  Nagoya Institute Of Technlogy

• Yokota Kazumasa

  Institute For New Generation Computer Technology Research Center

• MIYAZAKI NOBUYOSHI

  Oki Electric Industry Co., Ltd., Systems Laboratory

• HANIUDA HIROMI

  Oki Electric Industry Co., Ltd., Systems Laboratory

• Miyazaki Nobuyoshi

  Oki Electric Industry Co. Ltd. Systems Laboratory

• Haniuda Hiromi

  Oki Electric Industry Co. Ltd. Systems Laboratory

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