Abstract: "Several methods that transform queries to their equivalents in order to improve the performance of 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 discu...

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Bibliographische Detailangaben

Format:	Buch
Sprache:	English
Veröffentlicht:	Tokyo, Japan 1988
Schriftenreihe:	Shin-Sedai-Konpyūta-Gijutsu-Kaihatsu-Kikō <Tōkyō>: ICOT technical report 377
Schlagworte:	Deductive databases Expert systems (Computer science) Horn clauses Question-answering systems
Zusammenfassung:	Abstract: "Several methods that transform queries to their equivalents in order to improve the performance of 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 a transformation that preserves the answer to a query but allows the change of the least models of the database. Becuase the least model of the database is computed by 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 fundamental principles of first order logic such as resolution and submission, are shown. They include procedures called Horn clause transformations (HCT) by partial evaluation, HCT by substitution, and HCT by restrictor. Properties of these procedures are compared. The relationships of these procedures with other methods such as the distribution of selection and the magic set are discussed, and it is shown that the clause replacement is a common foundation of many transformation methods.
Beschreibung:	26 S.