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      To Form a More Perfect Union (Intersection, Difference)

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      Proceedings of the Fifth International Workshop on Database Programming Languages (DBPL-5)

      Database Programming Languages

      6-8 September 1995

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          Abstract

          The AQUA [16] query algebra allows user-defined equivalence relations as arguments to query operators that generalize standard set operations. These predicates determine what objects are included in the query result, and the duplicates that must be removed.

          While an expressive enhancement, the use of arbitrary equivalence relations to decide set membership can result in sets with counterintuitive behavior, and therefore can make queries return unreasonable results. In this paper, we show that equality predicates assume two roles with respect to sets. Distinguishers differentiate between set members and implicitly give meaning to standard set properties such as set equality. Constructors determine which object from input sets contribute to the query result. The requirements of distinguishers and constructors differ. AQUA’s set operators are problematic because they use constructors where distinguishers are required. We propose alternatives to AQUA’s set operators that address this limitation.

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          Equal rights for functional objects or, the more things change, the more they are the same

           Henry Baker (1993)
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            Rule languages and internal algebras for rule-based optimizers

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              The Joy of Sets

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                Author and article information

                Contributors
                Conference
                September 1995
                September 1995
                : 1-12
                Affiliations
                Brown University

                Providence, RI, USA
                Article
                10.14236/ewic/DBPL1995.5
                © Mitch Cherniack et al. Published by BCS Learning and Development Ltd. Proceedings of the Fifth International Workshop on Database Programming Languages, Gubbio, Umbria, Italy

                This work is licensed under a Creative Commons Attribution 4.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

                Proceedings of the Fifth International Workshop on Database Programming Languages
                DBPL-5
                5
                Gubbio, Umbria, Italy
                6-8 September 1995
                Electronic Workshops in Computing (eWiC)
                Database Programming Languages
                Product
                Product Information: 1477-9358BCS Learning & Development
                Self URI (journal page): https://ewic.bcs.org/
                Categories
                Electronic Workshops in Computing

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