2026-08-06T22:26:10Z https://drops.dagstuhl.de/oai

oai:drops-oai.dagstuhl.de:19804 2024-03-14T08:42:36Z ddc:004 open_access

Evaluating Graph Queries Using Semantic Treewidth Feier, Cristina Gogacz, Tomasz Murlak, Filip conjunctive two-way regular path queries fixed-parameter tractable evaluation semantic treewidth Datalog encoding optimization Unions of conjunctive two-way regular path queries (UC2RPQs) are a common abstraction of query languages for graph databases, much like unions of conjunctive queries (UCQs) in the relational case. As in the case of UCQs, their evaluation is NP-complete in combined complexity. Semantic tree-width, i.e. the minimal treewidth of equivalent queries, has been proposed as a candidate criterion to characterize fixed-parameter tractability of UC2RPQs. It was recently shown how to decide the semantic tree-width of a UC2RPQ, by constructing the best under-approximation of a given treewidth, in the form of a UC2RPQ of size doubly exponential in the size of the original query. This leads to an fpt algorithm for evaluating UC2RPQs of semantic TW k which runs in time doubly exponential in the size of the parameter, i.e. in the UC2RPQ. Here we describe a more efficient fpt algorithm for evaluating UC2RPQs of semantic treewidth k which runs in time singly exponential in the size of the parameter. We do this by a careful construction of a witness query which, while still being doubly exponential, can be represented as a Datalog program of bounded width and singly exponential size. Schloss Dagstuhl – Leibniz-Zentrum für Informatik Cristina Feier and Tomasz Gogacz and Filip Murlak 2024 Is Part Of LIPIcs, Volume 290, 27th International Conference on Database Theory (ICDT 2024) InProceedings Text doc-type:ResearchArticle publishedVersion application/pdf doi:10.4230/LIPIcs.ICDT.2024.22 urn:nbn:de:0030-drops-198048 https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2024.22 eng https://creativecommons.org/licenses/by/4.0/legalcode