eng
Schloss Dagstuhl – Leibniz-Zentrum für Informatik
Leibniz International Proceedings in Informatics
1868-8969
2019-07-04
104:1
104:15
10.4230/LIPIcs.ICALP.2019.104
article
Boundedness of Conjunctive Regular Path Queries (Track B: Automata, Logic, Semantics, and Theory of Programming)
Barceló, Pablo
1
2
https://orcid.org/0000-0003-2293-2653
Figueira, Diego
3
Romero, Miguel
4
Department of Computer Science, University of Chile, Santiago, Chile
IMFD, Santiago, Chile
CNRS & LaBRI, Talence, France
Department of Computer Science, University of Oxford, Oxford, UK
We study the boundedness problem for unions of conjunctive regular path queries with inverses (UC2RPQs). This is the problem of, given a UC2RPQ, checking whether it is equivalent to a union of conjunctive queries (UCQ). We show the problem to be ExpSpace-complete, thus coinciding with the complexity of containment for UC2RPQs. As a corollary, when a UC2RPQ is bounded, it is equivalent to a UCQ of at most triple-exponential size, and in fact we show that this bound is optimal. We also study better behaved classes of UC2RPQs, namely acyclic UC2RPQs of bounded thickness, and strongly connected UCRPQs, whose boundedness problem is, respectively, PSpace-complete and Pi_2^P-complete. Most upper bounds exploit results on limitedness for distance automata, in particular extending the model with alternation and two-wayness, which may be of independent interest.
https://drops.dagstuhl.de/storage/00lipics/lipics-vol132-icalp2019/LIPIcs.ICALP.2019.104/LIPIcs.ICALP.2019.104.pdf
regular path queries
boundedness
limitedness
distance automata