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.2022.10
URN: urn:nbn:de:0030-drops-158843
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Freydenberger, Dominik D. ; Thompson, Sam M.

Splitting Spanner Atoms: A Tool for Acyclic Core Spanners

LIPIcs-ICDT-2022-10.pdf (0.7 MB)


This paper investigates regex CQs with string equalities (SERCQs), a subclass of core spanners. As shown by Freydenberger, Kimelfeld, and Peterfreund (PODS 2018), these queries are intractable, even if restricted to acyclic queries. This previous result defines acyclicity by treating regex formulas as atoms. In contrast to this, we propose an alternative definition by converting SERCQs into FC-CQs - conjunctive queries in FC, a logic that is based on word equations. We introduce a way to decompose word equations of unbounded arity into a conjunction of binary word equations. If the result of the decomposition is acyclic, then evaluation and enumeration of results become tractable. The main result of this work is an algorithm that decides in polynomial time whether an FC-CQ can be decomposed into an acyclic FC-CQ. We also give an efficient conversion from synchronized SERCQs to FC-CQs with regular constraints. As a consequence, tractability results for acyclic relational CQs directly translate to a large class of SERCQs.

BibTeX - Entry

  author =	{Freydenberger, Dominik D. and Thompson, Sam M.},
  title =	{{Splitting Spanner Atoms: A Tool for Acyclic Core Spanners}},
  booktitle =	{25th International Conference on Database Theory (ICDT 2022)},
  pages =	{10:1--10:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-223-5},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{220},
  editor =	{Olteanu, Dan and Vortmeier, Nils},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{},
  URN =		{urn:nbn:de:0030-drops-158843},
  doi =		{10.4230/LIPIcs.ICDT.2022.10},
  annote =	{Keywords: Document spanners, information extraction, conjunctive queries}

Keywords: Document spanners, information extraction, conjunctive queries
Collection: 25th International Conference on Database Theory (ICDT 2022)
Issue Date: 2022
Date of publication: 19.03.2022
Supplementary Material: Audiovisual (Video of the Presentation):

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