On Equivalence and Cores for Incomplete Databases in Open and Closed Worlds

no code implementations • 14 Jan 2020 • Henrik Forssell, Evgeny Kharlamov, Evgenij Thorstensen

However, for Closed Powerset semantics we show that one can find, for any incomplete database, a unique finite set of its subinstances which are subinstances (up to renaming of nulls) of all instances semantically equivalent to the original incomplete one.

Generating Ontologies from Templates: A Rule-Based Approach for Capturing Regularity

no code implementations • 27 Sep 2018 • Henrik Forssell, Christian Kindermann, Daniel P. Lupp, Uli Sattler, Evgenij Thorstensen

We present a second-order language that can be used to succinctly specify ontologies in a consistent and transparent manner.

Negation

Mapping Data to Ontologies with Exceptions Using Answer Set Programming

no code implementations • 7 Jul 2016 • Daniel P. Lupp, Evgenij Thorstensen

In ontology-based data access, databases are connected to an ontology via mappings from queries over the database to queries over the ontology.

Structural Decompositions for Problems with Global Constraints

no code implementations • 9 Feb 2015 • Evgenij Thorstensen

We show that when the number of solutions to a CSP instance is bounded in key parts of the problem, structural restrictions can be used to derive new tractable classes.

Tractable Combinations of Global Constraints

no code implementations • 10 Jul 2013 • David A. Cohen, Peter G. Jeavons, Evgenij Thorstensen, Stanislav Živný

We study the complexity of constraint satisfaction problems involving global constraints, i. e., special-purpose constraints provided by a solver and represented implicitly by a parametrised algorithm.

Lifting Structural Tractability to CSP with Global Constraints

no code implementations • 6 Jul 2013 • Evgenij Thorstensen

This allows us to lift these restrictions to the global case, and identify new tractable classes of CSPs with global constraints.