2026-07-23T13:56:16Z https://drops.dagstuhl.de/oai

oai:drops-oai.dagstuhl.de:11868 2024-03-06T10:48:53Z ddc:004 open_access

A Trichotomy for Regular Trail Queries Martens, Wim Niewerth, Matthias Trautner, Tina Regular languages query languages path queries graph databases databases complexity trails simple paths Regular path queries (RPQs) are an essential component of graph query languages. Such queries consider a regular expression r and a directed edge-labeled graph G and search for paths in G for which the sequence of labels is in the language of r. In order to avoid having to consider infinitely many paths, some database engines restrict such paths to be trails, that is, they only consider paths without repeated edges. In this paper we consider the evaluation problem for RPQs under trail semantics, in the case where the expression is fixed. We show that, in this setting, there exists a trichotomy. More precisely, the complexity of RPQ evaluation divides the regular languages into the finite languages, the class T_tract (for which the problem is tractable), and the rest. Interestingly, the tractable class in the trichotomy is larger than for the trichotomy for simple paths, discovered by Bagan et al. [Bagan et al., 2013]. In addition to this trichotomy result, we also study characterizations of the tractable class, its expressivity, the recognition problem, closure properties, and show how the decision problem can be extended to the enumeration problem, which is relevant to practice. Schloss Dagstuhl – Leibniz-Zentrum für Informatik Wim Martens and Matthias Niewerth and Tina Trautner 2020 Is Part Of LIPIcs, Volume 154, 37th International Symposium on Theoretical Aspects of Computer Science (STACS 2020) InProceedings Text doc-type:ResearchArticle publishedVersion application/pdf doi:10.4230/LIPIcs.STACS.2020.7 urn:nbn:de:0030-drops-118681 https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2020.7 eng https://creativecommons.org/licenses/by/3.0/legalcode