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dc.contributor.authorCalvanese D
dc.contributor.authorDe Giacomo G
dc.contributor.authorLenzerini M
dc.contributor.authorVardi M
dc.contributor.editor
dc.date.accessioned2018-09-03T08:03:13Z
dc.date.available2018-09-03T08:03:13Z
dc.date.issued2012
dc.identifier.issn2150-8097
dc.identifier.urihttp://dx.doi.org/http://www.vldb.org/pvldb/vol6.html
dc.identifier.urihttp://hdl.handle.net/10863/5941
dc.description.abstractSchema mappings establish a correspondence between data stored in two databases, called source and target respectively. Query processing under schema mappings has been investigated extensively in the two cases where each target atom is mapped to a query over the source (called GAV, global-as-view), and where each source atom is mapped to a query over the target (called LAV, local-as-view). The general case, called GLAV, in which queries over the source are mapped to queries over the target, has attracted a lot of attention recently, especially for data exchange. However, query processing for GLAV mappings has been considered only for the basic service of query answering, and mainly in the context of conjunctive queries (CQs) in relational databases. In this paper we study query processing for GLAV mappings in a wider sense, considering not only query answering, but also query rewriting, perfectness (the property of a rewriting to compute exactly the certain answers), and query containment relative to a mapping. We deal both with the relational case, and with graph databases, where the basic querying mechanism is that or regular path queries. Query answering in GLAV can be smoothly reduced to a combination of the LAV and GAV cases, and for CQs this reduction can be exploited also for the remaining query processing tasks. In contrast, as we show, GLAV query processing for graph databases is non-trivial and requires new insights and techniques. We obtain upper bounds for answering, rewriting, and perfectness, and show decidability of relative containment.en_US
dc.language.isoenen_US
dc.rights
dc.titleQuery Processing under GLAV Mappings for Relational and Graph Databasesen_US
dc.typeArticleen_US
dc.date.updated2018-09-03T07:02:34Z
dc.publication.title
dc.language.isiEN-GB
dc.journal.titleProceedings of the VLDB Endowment
dc.description.fulltextopenen_US


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