Query containment under bag and bag-set semantics

Afrati, FN; Damigos, M; Gergatsoulis, M

dc.contributor.author	Afrati, FN	en
dc.contributor.author	Damigos, M	en
dc.contributor.author	Gergatsoulis, M	en
dc.date.accessioned	2014-03-01T01:34:23Z
dc.date.available	2014-03-01T01:34:23Z
dc.date.issued	2010	en
dc.identifier.issn	0020-0190	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/20721
dc.subject	Bag semantics	en
dc.subject	Bag-set semantics	en
dc.subject	Conjunctive queries	en
dc.subject	Databases	en
dc.subject	Query containment	en
dc.subject.classification	Computer Science, Information Systems	en
dc.subject.other	Bag-set semantics	en
dc.subject.other	Complexity results	en
dc.subject.other	Conjunctive queries	en
dc.subject.other	Data integration	en
dc.subject.other	Databases	en
dc.subject.other	Query containment	en
dc.subject.other	Query optimization	en
dc.subject.other	Query reformulation	en
dc.subject.other	Real applications	en
dc.subject.other	Research fields	en
dc.subject.other	Research topics	en
dc.subject.other	Set semantics	en
dc.subject.other	Data handling	en
dc.subject.other	Semantics	en
dc.subject.other	Query languages	en
dc.title	Query containment under bag and bag-set semantics	en
heal.type	journalArticle	en
heal.identifier.primary	10.1016/j.ipl.2010.02.017	en
heal.identifier.secondary	http://dx.doi.org/10.1016/j.ipl.2010.02.017	en
heal.language	English	en
heal.publicationDate	2010	en
heal.abstract	Conjunctive queries (CQs) are at the core of query languages encountered in many logic-based research fields such as Al, or database systems. The majority of existing work assumes set semantics but often in real applications the manipulation of duplicate tuples is required. One of the major problems that arises as part of advanced features of query optimization, data integration, query reformulation and many other research topics is testing for containment of such queries. In this work, we investigate the complexity of query containment problem for CQs under bag semantics (i.e. duplicate tuples are allowed in both the database and the results of queries) and under bag-set semantics (i.e. duplicates are allowed in the result of the queries but not in the database). We derive complexity results for these problems for five major subclasses of CQs; and we also find necessary conditions for CQ query containment. The general case of these problems remains open. (C) 2010 Elsevier B.V. All rights reserved.	en
heal.publisher	ELSEVIER SCIENCE BV	en
heal.journalName	Information Processing Letters	en
dc.identifier.doi	10.1016/j.ipl.2010.02.017	en
dc.identifier.isi	ISI:000277661100003	en
dc.identifier.volume	110	en
dc.identifier.issue	10	en
dc.identifier.spage	360	en
dc.identifier.epage	369	en