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政大機構典藏 > 資訊學院 > 資訊科學系 > 期刊論文 > Item 140.119/69126

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題名:	Manipulation of exclusive disjunctive data in relational databases
作者:	陳良弼 Chiu,Jui-Shang;Chen,Arbee L.P.
貢獻者:	資科系
關鍵詞:	Incomplete information;Disjunctive information;Partial values;Query language semantics;Relational algebra;Relational databases
日期:	1997
上傳時間:	2014-08-21 14:47:37 (UTC+8)
摘要:	In this paper, we propose an extended relational model, named Pv-table, for representing exclusive disjunctive data (i.e., there exists a set of possible values for a data item, and exactly one of the possible values is true) by associating partial values and variables with attributes. While a partial value denotes the set of possible values, a variable serves as an identifier for the true value of the data item. Identifiers can be used to determine the equi-relationship among partial values. The relational operators are extended to manipulate Pv-tables. We show that the set-based query evaluation on Pv-tables is sound and complete for queries consisting of extended selection, union, intersection, Cartesian product and join. We also show that useful algebraic properties are preserved in our model. A disjunctive (resp. conjunctive) query can be replaced by the extended union (resp. intersection) of the two corresponding subqueries. These properties provide a more natural interpretation of queries. They also facilitate query decomposition process for optimizing distributed queries. These properties are not preserved for many other extended models.
關聯:	Data & Knowledge Engineering,22(1),39-65
資料類型:	article
顯示於類別:	[資訊科學系] 期刊論文

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