License: Creative Commons Attribution 4.0 International license (CC BY 4.0)
When quoting this document, please refer to the following
DOI: 10.4230/LIPIcs.ICDT.2023.15
URN: urn:nbn:de:0030-drops-177575
URL: http://dagstuhl.sunsite.rwth-aachen.de/volltexte/2023/17757/
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Figueira, Diego ; Morvan, Rémi

Approximation and Semantic Tree-Width of Conjunctive Regular Path Queries

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LIPIcs-ICDT-2023-15.pdf (4 MB)

Abstract

We show that the problem of whether a query is equivalent to a query of tree-width k is decidable, for the class of Unions of Conjunctive Regular Path Queries with two-way navigation (UC2RPQs). A previous result by Barceló, Romero, and Vardi [Pablo Barceló et al., 2016] has shown decidability for the case k = 1, and here we show that decidability in fact holds for any arbitrary k > 1. The algorithm is in 2ExpSpace, but for the restricted but practically relevant case where all regular expressions of the query are of the form a^* or (a_1 + ... + a_n) we show that the complexity of the problem drops to Π^p_2.
We also investigate the related problem of approximating a UC2RPQ by queries of small tree-width. We exhibit an algorithm which, for any fixed number k, builds the maximal under-approximation of tree-width k of a UC2RPQ. The maximal under-approximation of tree-width k of a query q is a query q' of tree-width k which is contained in q in a maximal and unique way, that is, such that for every query q'' of tree-width k, if q'' is contained in q then q'' is also contained in q'.

BibTeX - Entry

@InProceedings{figueira_et_al:LIPIcs.ICDT.2023.15,
  author =	{Figueira, Diego and Morvan, R\'{e}mi},
  title =	{{Approximation and Semantic Tree-Width of Conjunctive Regular Path Queries}},
  booktitle =	{26th International Conference on Database Theory (ICDT 2023)},
  pages =	{15:1--15:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-270-9},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{255},
  editor =	{Geerts, Floris and Vandevoort, Brecht},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/opus/volltexte/2023/17757},
  URN =		{urn:nbn:de:0030-drops-177575},
  doi =		{10.4230/LIPIcs.ICDT.2023.15},
  annote =	{Keywords: graph databases, conjunctive regular path queries, semantic optimization, tree-width, containment, approximation}
}

Keywords: graph databases, conjunctive regular path queries, semantic optimization, tree-width, containment, approximation
Collection: 26th International Conference on Database Theory (ICDT 2023)
Issue Date: 2023
Date of publication: 17.03.2023

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