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Fragments of Bag Relational Algebra: Expressiveness and Certain Answers

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http://drops.dagstuhl.de/opus/volltexte/2019/10310/
Original languageEnglish
Title of host publication22nd International Conference on Database Theory (ICDT 2019)
EditorsPablo Barcelo, Marco Calautti
Number of pages16
ISBN (Electronic)978-3-95977-101-6
DOIs
Publication statusPublished - 19 Mar 2019
Event22nd International Conference on Database Theory - Lisbon, Portugal
Duration: 26 Mar 201929 Mar 2019
http://edbticdt2019.inesc-id.pt/

Publication series

NameLIPICS
Volume127
ISSN (Electronic)1868-8969

Conference

Conference22nd International Conference on Database Theory
Abbreviated titleICDT 2019
CountryPortugal
CityLisbon
Period26/03/1929/03/19
Internet address

Abstract

While all relational database systems are based on the bag data model, much of theoretical research still views relations as sets. Recent attempts to provide theoretical foundations for modern data management problems under the bag semantics concentrated on applications that need to deal with incomplete relations, i.e., relations populated by constants and nulls. Our goal is to provide a complete characterization of the complexity of query answering over such relations in fragments of bag relational algebra.The main challenges we face are twofold. First, bag relational algebra has more operations than its set analog (e.g., additive union, max-union, min-intersection, duplicate elimination) and the relationship between various fragments is not fully known. Thus we first fill this gap. Second,we look at query answering over incomplete data which again is more complex than in the set case: rather than certainty and possibility of answers, we now have numerical information about occurrences of tuples. We then fully classify the complexity of finding this information in all the fragments of bag relational algebra.

Event

22nd International Conference on Database Theory

26/03/1929/03/19

Lisbon, Portugal

Event: Conference

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