1998 Fiscal Year Final Research Report Summary
Research or Processing queries Containing Backward Narigation of Path Expressions in Complex Object Models
| Project/Area Number |
09680399
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
情報システム学(含情報図書館学)
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| Research Institution | Nara Institute of Science and Technology |
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Principal Investigator |
ITO Nara Institute of Science and Technology, Professor, 情報科学研究科, 教授 (90127184)
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| Co-Investigator(Kenkyū-buntansha) |
NAKANISHI Nara Institute of Science and Technology, Research Associate, 情報科学研究科, 助手 (60263232)
ISHIHARA Nara Institute of Science and Technology, Research Associate, 情報科学研究科, 助手 (00263434)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Object-Oriented Database / Path Expression / Backward Narigation / Query Processing |
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| Research Abstract |
1. A database schema in object-oriented databases is, in general, more flexible than one in relational databases, since an ISA hierarchy among classes can be defined and an object can have not only a simple value but another object as its attribute. Furthermore, a more complex query can be expressed using sophisticated path expression. In this research, we aim to develop a method for an efficient process of queries containing backward navigation in path expressions and have had the following results.
2. In order to process a given query in a usual way, the query must be transformed into a query containing no backward navigation. We have had the following results on this transformation.
(1) We introduce an algebraic query language that is independent of any specific query language. Under the language, we have shown that every algebra expression with backward navigation .has an equivalent algebra expression without backward navigation.
(2) We have developed a polynomial time algorithm that transforms an algebra expression with back-ward navigation into an equivalent one without backward navigation.
3. A navigability problem is to decide, given a class and a path expression with backward navigation, whether there is a database in which we can navigate from an object in the class to another object through the path expression. We have developed a polynomial time algorithm for deciding the navigavility problem.
4. In the case where a given path expression contains closures, we have developed a polynomial time algorithm for deciding the navigability problem.
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