How to Approximate Ontology-Mediated Queries

07/12/2021
by   Anneke Haga, et al.
0

We introduce and study several notions of approximation for ontology-mediated queries based on the description logics ALC and ALCI. Our approximations are of two kinds: we may (1) replace the ontology with one formulated in a tractable ontology language such as ELI or certain TGDs and (2) replace the database with one from a tractable class such as the class of databases whose treewidth is bounded by a constant. We determine the computational complexity and the relative completeness of the resulting approximations. (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. While approximations of kind (1) also reduce the combined complexity, this tends to not be the case for approximations of kind (2). In some cases, the combined complexity even increases.

READ FULL TEXT

page 1

page 2

page 3

page 4

05/04/2022

Ontology-Mediated Querying on Databases of Bounded Cliquewidth

We study the evaluation of ontology-mediated queries (OMQs) on databases...
03/17/2020

When is Ontology-Mediated Querying Efficient?

In ontology-mediated querying, description logic (DL) ontologies are use...
01/21/2020

A Journey into Ontology Approximation: From Non-Horn to Hon

We study complete approximations of an ontology formulated in a non-Horn...
01/21/2020

A Journey into Ontology Approximation: From Non-Horn to Horn

We study complete approximations of an ontology formulated in a non-Horn...
03/17/2022

Efficiently Enumerating Answers to Ontology-Mediated Queries

We study the enumeration of answers to ontology-mediated queries (OMQs) ...
03/30/2019

Ontology Focusing: Knowledge-enriched Databases on Demand

We propose a novel framework to facilitate the on-demand design of data-...
07/01/2021

Computing CQ lower-bounds over OWL 2 through approximation to RSA

Conjunctive query (CQ) answering over knowledge bases is an important re...