Publication details
Quantified conjunctive queries on partially ordered sets
| Authors | |
|---|---|
| Year of publication | 2016 |
| Type | Article in Periodical |
| Magazine / Source | Theoretical Computer Science |
| MU Faculty or unit | |
| Citation | |
| Doi | http://dx.doi.org/10.1016/j.tcs.2016.01.010 |
| Field | Informatics |
| Keywords | Quantified conjunctive queries; Posets; Parameterized complexity; Model checking |
| Description | We study the computational problem of checking whether a quantified conjunctive query (a first-order sentence built using only conjunction as Boolean connective) is true in a finite poset (a reflexive, antisymmetric, and transitive directed graph). We prove that the problem is already NP-hard on a certain fixed poset, and investigate structural properties of posets yielding fixed-parameter tractability when the problem is parameterized by the query. Our main algorithmic result is that model checking quantified conjunctive queries on posets is fixed-parameter tractable when parameterized by the sentence and the width of the poset (the maximum size of a subset of pairwise incomparable elements). We complement our algorithmic result by complexity results with respect to classes of finite posets in a hierarchy of natural poset invariants, establishing its tightness in this sense. (C) 2016 Elsevier B.V. All rights reserved. |