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https://ah.lib.nccu.edu.tw/handle/140.119/69126
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: | 21-Aug-2014 | 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 |
Appears in Collections: | 期刊論文 |
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