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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/21588

Title: Mapping-equivalence and oid-equivalence of single-function object-creating conjunctive queries
Authors: Bonifati, Angela
Nutt, Werner
Torlone, Riccardo
Van den Bussche, Jan
Issue Date: 2016
Publisher: SPRINGER
Citation: VLDB JOURNAL, 25 (3), p. 381-397
Abstract: Conjunctive database queries have been extended with a mechanism for object creation to capture important applications such as data exchange, data integration, and ontology-based data access. Object creation generates new object identifiers in the result that do not belong to the set of constants in the source database. The new object identifiers can be also seen as Skolem terms. Hence, object-creating conjunctive queries can also be regarded as restricted second-order tuple-generating dependencies (SO-tgds), considered in the data exchange literature. In this paper, we focus on the class of single-function object-creating conjunctive queries, or sifo CQs for short. The single-function symbol can be used only once in the head of the query. We give a new characterization for oid-equivalence of sifo CQs that is simpler than the one given by Hull and Yoshikawa and places the problem in the complexity class NP. Our characterization is based on Cohen's equivalence notions for conjunctive queries with multiplicities. We also solve the logical entailment problem for sifo CQs, showing that also this problem belongs to NP. Results by Pichler et al. have shown that logical equivalence for more general classes of SO-tgds is either undecidable or decidable with as yet unknown complexity upper bounds.
Notes: [Bonifati, Angela] Univ Lyon 1, LIRIS, F-69365 Lyon, France. [Nutt, Werner] Free Univ Bozen Bolzano, Bolzano, Italy. [Torlone, Riccardo] Univ Rome Tre, I-00146 Rome, Italy. [Van den Bussche, Jan] Hasselt Univ, Hasselt, Belgium. [Van den Bussche, Jan] Transnat Univ Limburg, Hasselt, Belgium.
URI: http://hdl.handle.net/1942/21588
DOI: 10.1007/s00778-016-0421-x
ISI #: 000376263400005
ISSN: 1066-8888
Category: A1
Type: Journal Contribution
Validation: ecoom, 2017
Appears in Collections: Research publications

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