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http://hdl.handle.net/1942/26657
Title: | First-order definable counting-only queries | Authors: | HELLINGS, Jelle GYSSENS, Marc Van Gucht, Dirk Wu, Yuqing |
Issue Date: | 2018 | Publisher: | Springer International Publishing AG | Source: | Ferrarotti, Flavio; Woltran, Stefan (Ed.). Foundations of Information and Knowledge Systems 10th International Symposium, FoIKS 2018, Budapest, Hungary, May 14–18, 2018, Proceedings, Springer International Publishing AG,p. 225-243 | Series/Report: | Lecture Notes in Computer Science | Series/Report no.: | 1083 | Abstract: | For several practical queries on bags of sets of objects, the answer does not depend on the precise composition of these sets, but only on the number of sets to which each object belongs. This is the case k=1 for the more general situation where the query answer only depends on the number of sets to which each group of at most k objects belongs. We call such queries k-counting-only. Here, we focus on k-SyCALC, k-counting-only queries that are first-order definable. As kSyCALC is semantically defined, however, it is not surprising that it is already undecidable whether a first-order query is in 1-SyCALC. Therefore, we introduce SimpleCALC-k, a syntactically defined (strict) fragment of k-SyCALC. It turns out that many practical queries in k-SyCALC can already be expressed in SimpleCALC-k. We prove that the k-countingonly queries form a non-collapsing hierarchy: for every k, there exist (k+1)-counting-only queries that are not k-counting-only. This result specializes to both SimpleCALC-k and k-SyCALC. Finally, we establish a strong dichotomy between 1-SyCALC and SimpleCALC-k on the one hand and 2-SyCALC on the other hand by showing that satisfiability, validity, query containment, and query equivalence are decidable for the former two languages, but not for the latter one. | Document URI: | http://hdl.handle.net/1942/26657 | ISBN: | 9783319900490 | DOI: | 10.1007/978-3-319-90050-6_13 | ISI #: | 000546329500013 | Category: | C1 | Type: | Proceedings Paper | Validations: | ecoom 2021 |
Appears in Collections: | Research publications |
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foiks2018_2_paper.pdf | Peer-reviewed author version | 444.1 kB | Adobe PDF | View/Open |
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