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http://hdl.handle.net/1942/30770
Title: | Comparing the expressiveness of downward fragments of the relation algebra with transitive closure on trees | Authors: | HELLINGS, Jelle GYSSENS, Marc Wu, Yuqing Van Gucht, Dirk VAN DEN BUSSCHE, Jan VANSUMMEREN, Stijn Fletcher, George H. L. |
Issue Date: | 2020 | Publisher: | PERGAMON-ELSEVIER SCIENCE LTD | Source: | Information Systems, 89 (Art N° 101467) | Abstract: | Motivated by the continuing interest in the tree data model, we study the expressive power of downward navigational query languages on trees and chains. Basic navigational queries are built from the identity relation and edge relations using composition and union. We study the effects on relative expressiveness when we add transitive closure, projections, coprojections, intersection, and difference; this for Boolean queries and path queries on labeled and unlabeled structures. In all cases, we present the complete Hasse diagram. In particular, we establish, for each query language fragment that we study on trees, whether it is closed under difference and intersection. (C) 2019 Elsevier Ltd. All rights reserved. | Notes: | Gyssens, M (reprint author), Hasselt Univ, Martelarenlaan 42, Hasselt, Belgium. jhellings@ucdavis.edu; marc.gyssens@uhasselt.be; melanie.wu@pomona.edu; vgucht@cs.indiana.edu; jan.vandenbussche@uhasselt.be; stijn.vansummeren@ulb.ac.be; g.h.l.fletcher@tue.nl |
Other: | Gyssens, M (reprint author), Hasselt Univ, Martelarenlaan 42, Hasselt, Belgium. jhellings@ucdavis.edu; marc.gyssens@uhasselt.be; melanie.wu@pomona.edu; vgucht@cs.indiana.edu; jan.vandenbussche@uhasselt.be; stijn.vansummeren@ulb.ac.be; g.h.l.fletcher@tue.nl | Keywords: | Tree data model;Relational calculus with transitive closure;Downward query language fragments;Path queries;Boolean queries;Relative expressive power | Document URI: | http://hdl.handle.net/1942/30770 | ISSN: | 0306-4379 | e-ISSN: | 1873-6076 | DOI: | 10.1016/j.is.2019.101467 | ISI #: | WOS:000514004100002 | Rights: | 2019 Elsevier Ltd. All rights reserved. | Category: | A1 | Type: | Journal Contribution | Validations: | ecoom 2021 |
Appears in Collections: | Research publications |
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File | Description | Size | Format | |
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is2019_paper.pdf | Non Peer-reviewed author version | 470.65 kB | Adobe PDF | View/Open |
hellings.pdf Restricted Access | Published version | 740.55 kB | Adobe PDF | View/Open Request a copy |
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