Determinacy and query rewriting for conjunctive queries and views

Afrati, FN

dc.contributor.author	Afrati, FN	en
dc.date.accessioned	2014-03-01T11:45:10Z
dc.date.available	2014-03-01T11:45:10Z
dc.date.issued	2011	en
dc.identifier.issn	0304-3975	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/37266
dc.subject	Chain queries	en
dc.subject	Conjunctive queries	en
dc.subject	Determinacy	en
dc.subject	First order logic	en
dc.subject	Path queries	en
dc.subject	Query answering	en
dc.subject	Query rewriting	en
dc.subject	Views	en
dc.subject.classification	Computer Science, Theory & Methods	en
dc.subject.other	Conjunctive queries	en
dc.subject.other	Determinacy	en
dc.subject.other	First order logic	en
dc.subject.other	Path queries	en
dc.subject.other	Query answering	en
dc.subject.other	Query rewriting	en
dc.subject.other	Views	en
dc.subject.other	Equivalence classes	en
dc.subject.other	Query languages	en
dc.title	Determinacy and query rewriting for conjunctive queries and views	en
heal.type	other	en
heal.identifier.primary	10.1016/j.tcs.2010.12.031	en
heal.identifier.secondary	http://dx.doi.org/10.1016/j.tcs.2010.12.031	en
heal.language	English	en
heal.publicationDate	2011	en
heal.abstract	Answering queries using views is the problem which examines how to derive the answers to a query when we only have the answers to a set of views. Constructing rewritings is a widely studied technique to derive those answers. In this paper we consider the problem of the existence of rewritings in the case where the answers to the views uniquely determine the answers to the query. Specifically, we say that a view set V determines a query Q if for any two databases D-1, D-2 it holds: V(D-1) = V(D-2) implies Q(D-1) = Q (D-2). We consider the case where query and views are defined by conjunctive queries and investigate the question: If a view set V determines a query Q, is there an equivalent rewriting of Q using V? We present here interesting cases where there are such rewritings in the language of conjunctive queries. Interestingly, we identify a class of conjunctive queries, CQ(path), for which a view set can produce equivalent rewritings for "almost all" queries which are determined by this view set. We introduce a problem which relates determinacy to query equivalence. We show that there are cases where restricted results can carry over to broader classes of queries. (C) 2010 Elsevier B.V. All rights reserved.	en
heal.publisher	ELSEVIER SCIENCE BV	en
heal.journalName	Theoretical Computer Science	en
dc.identifier.doi	10.1016/j.tcs.2010.12.031	en
dc.identifier.isi	ISI:000287791400004	en
dc.identifier.volume	412	en
dc.identifier.issue	11	en
dc.identifier.spage	1005	en
dc.identifier.epage	1021	en