License: Creative Commons Attribution 3.0 Unported license (CC BY 3.0)
When quoting this document, please refer to the following
DOI: 10.4230/LIPIcs.ICDT.2015.110
URN: urn:nbn:de:0030-drops-49804
URL: http://dagstuhl.sunsite.rwth-aachen.de/volltexte/2015/4980/
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Chen, Hubie ; Mengel, Stefan

A Trichotomy in the Complexity of Counting Answers to Conjunctive Queries

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Abstract

Conjunctive queries are basic and heavily studied database queries; in relational algebra, they are the select-project-join queries. In this article, we study the fundamental problem of counting, given a conjunctive query and a relational database, the number of answers to the query on the database. In particular, we study the complexity of this problem relative to sets of conjunctive queries. We present a trichotomy theorem, which shows essentially that this problem on a set of conjunctive queries is either tractable, equivalent to the parameterized CLIQUE problem, or as hard as the parameterized counting CLIQUE problem; the criteria describing which of these situations occurs is simply stated, in terms of graph-theoretic conditions.

BibTeX - Entry

@InProceedings{chen_et_al:LIPIcs:2015:4980,
  author =	{Hubie Chen and Stefan Mengel},
  title =	{{A Trichotomy in the Complexity of Counting Answers to Conjunctive Queries}},
  booktitle =	{18th International Conference on Database Theory (ICDT 2015)},
  pages =	{110--126},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-79-8},
  ISSN =	{1868-8969},
  year =	{2015},
  volume =	{31},
  editor =	{Marcelo Arenas and Mart{\'i}n Ugarte},
  publisher =	{Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{http://drops.dagstuhl.de/opus/volltexte/2015/4980},
  URN =		{urn:nbn:de:0030-drops-49804},
  doi =		{10.4230/LIPIcs.ICDT.2015.110},
  annote =	{Keywords: database theory, query answering, conjunctive queries, counting complexity}
}

Keywords: database theory, query answering, conjunctive queries, counting complexity
Collection: 18th International Conference on Database Theory (ICDT 2015)
Issue Date: 2015
Date of publication: 19.03.2015

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