Rewriting queries using views with negation

Afrati, F; Pavlaki, V

dc.contributor.author	Afrati, F	en
dc.contributor.author	Pavlaki, V	en
dc.date.accessioned	2014-03-01T01:25:05Z
dc.date.available	2014-03-01T01:25:05Z
dc.date.issued	2006	en
dc.identifier.issn	09217126	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/17535
dc.relation.uri	http://www.scopus.com/inward/record.url?eid=2-s2.0-33748487630&partnerID=40&md5=b45e699ede89d703b04f75bafdea7f61	en
dc.relation.uri	http://www.informatik.uni-trier.de/~ley/db/journals/aicom/aicom19.html#AfratiP06	en
dc.relation.uri	http://iospress.metapress.com/openurl.asp?genre=article&issn=0921-7126&volume=19&issue=3&spage=229	en
dc.subject	Data integration	en
dc.subject	Negation	en
dc.subject	Query rewritings	en
dc.subject.other	Algorithms	en
dc.subject.other	Artificial intelligence	en
dc.subject.other	Computation theory	en
dc.subject.other	Data reduction	en
dc.subject.other	Database systems	en
dc.subject.other	Problem solving	en
dc.subject.other	Data integration	en
dc.subject.other	Negation	en
dc.subject.other	Query rewritings	en
dc.subject.other	Query languages	en
dc.title	Rewriting queries using views with negation	en
heal.type	journalArticle	en
heal.publicationDate	2006	en
heal.abstract	Data integration and query reformulation are classical examples of problems that require techniques developed in both AI and database systems fields. In this work we address the problem of rewriting queries using views which has many applications. In particular, we consider queries and views that are conjunctive queries with safe negation (CQNs). We prove that given a CQN query and a set of CQN views, finding equivalent rewritings is decidable in both cases where the rewriting is in the language of CQNs or unions of CQNs. We prove decidability by giving upper bounds on the number of subgoals of the rewritings. We limit the search space of potential equivalent CQN rewritings and Maximally Contained CQN Rewritings (MCRs) to the language of unions of CQs in the case where the query is CQ. Finally, we give a sound and complete algorithm for finding equivalent rewritings in the language of unions of CQNs and we prove that if we consider the rewritings without negated subgoals, then they compute only certain answers under the OWA. Of independent interest is a simple test for checking containment between two unions of CQNs. © 2006 - IOS Press and the authors. All rights reserved.	en
heal.journalName	AI Communications	en
dc.identifier.volume	19	en
dc.identifier.issue	3	en
dc.identifier.spage	229	en
dc.identifier.epage	237	en