Ehemalige Mitarbeiter

Dr. Stefan Mengel

Kontakt
CRIL-CNRS/Université d'Artois
Faculté des Sciences Jean Perrin
rue Jean Souvraz, S.P. 18
F-62307 LENS Cedex
FRANCE

Persönliche Homepage
www.cril.univ-artois.fr/~mengel/

The Complexity of Weighted Counting for Acyclic Conjunctive Queries
Zitatschlüssel	DM-The-Complexity-Of-Weighted-Counting-For-Acyclic-Conjunctive-Queries
Autor	Arnaud Durand and Stefan Mengel
Seiten	277-296
Jahr	2014
DOI	10.1016/j.jcss.2013.08.001
Journal	Journal of Computer and System Sciences
Jahrgang	80
Nummer	1
Zusammenfassung	This paper is a study of weighted counting of the solutions of acyclic conjunctive queries (ACQ). The unweighted quantifier free version of this problem is known to be tractable (for combined complexity), but it is also known that introducing even a single quantified variable makes it #P-hard. We first show that weighted counting for quantifier-free ACQ is still tractable and that even minimalistic extensions of the problem lead to hard cases. We then introduce a new parameter for quantified queries that permits to isolate large island of tractability. We show that, up to a standard assumption from parameterized complexity, this parameter fully characterizes tractable subclasses for counting weighted solutions of ACQ queries. Thus we completely determine the tractability frontier for weighted counting for ACQ.