Ontology-Mediated Querying on Databases of Bounded Cliquewidth

no code implementations • 4 May 2022 • Carsten Lutz, Leif Sabellek, Lukas Schulze

We study the evaluation of ontology-mediated queries (OMQs) on databases of bounded cliquewidth from the viewpoint of parameterized complexity theory.

How to Approximate Ontology-Mediated Queries

no code implementations • 12 Jul 2021 • Anneke Haga, Carsten Lutz, Leif Sabellek, Frank Wolter

(Almost) all of them reduce the data complexity from coNP-complete to PTime, in some cases even to fixed-parameter tractable and to linear time.

Query Expressibility and Verification in Ontology-Based Data Access

no code implementations • 18 Nov 2020 • Carsten Lutz, Johannes Marti, Leif Sabellek

In ontology-based data access, multiple data sources are integrated using an ontology and mappings.

A Complete Classification of the Complexity and Rewritability of Ontology-Mediated Queries based on the Description Logic EL

no code implementations • 29 Apr 2019 • Carsten Lutz, Leif Sabellek

We provide an ultimately fine-grained analysis of the data complexity and rewritability of ontology-mediated queries (OMQs) based on an EL ontology and a conjunctive query (CQ).

General Classification