no code implementations • 23 May 2024 • Veeti Ahvonen, Damian Heiman, Antti Kuusisto, Carsten Lutz
This implies that recurrent GNNs with reals and floats have the same expressive power over MSO-definable properties and shows that, for such properties, also recurrent GNNs with reals are characterized by a (finitary!)
no code implementations • 18 Sep 2023 • Maurice Funk, Simon Hosemann, Jean Christoph Jung, Carsten Lutz
We present a method for automatically constructing a concept hierarchy for a given domain by querying a large language model.
no code implementations • 7 Jun 2023 • Carsten Lutz, Quentin Manière, Robin Nolte
Circumscription is one of the main approaches for defining non-monotonic description logics (DLs).
no code implementations • 6 Jun 2023 • Carsten Lutz, Lukas Schulze
Ontologies often require knowledge representation on multiple levels of abstraction, but description logics (DLs) are not well-equipped for supporting this.
1 code implementation • 15 May 2023 • Balder ten Cate, Maurice Funk, Jean Christoph Jung, Carsten Lutz
We propose bounded fitting as a scheme for learning description logic concepts in the presence of ontologies.
no code implementations • 22 Aug 2022 • Balder ten Cate, Maurice Funk, Jean Christoph Jung, Carsten Lutz
This note serves three purposes: (i) we provide a self-contained exposition of the fact that conjunctive queries are not efficiently learnable in the Probably-Approximately-Correct (PAC) model, paying clear attention to the complicating fact that this concept class lacks the polynomial-size fitting property, a property that is tacitly assumed in much of the computational learning theory literature; (ii) we establish a strong negative PAC learnability result that applies to many restricted classes of conjunctive queries (CQs), including acyclic CQs for a wide range of notions of "acyclicity"; (iii) we show that CQs (and UCQs) are efficiently PAC learnable with membership queries.
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.
no code implementations • 29 Apr 2022 • Maurice Funk, Jean Christoph Jung, Carsten Lutz
We study ELI queries (ELIQs) in the presence of ontologies formulated in the description logic DL-Lite.
no code implementations • 11 Feb 2022 • Jean Christoph Jung, Carsten Lutz, Jerzy Macinkowski
We study the problem to decide, given sets T1, T2 of tuple-generating dependencies (TGDs), also called existential rules, whether T2 is a conservative extension of T1.
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.
no code implementations • 18 May 2021 • Maurice Funk, Jean Christoph Jung, Carsten Lutz
We also show that EL-concepts are not polynomial query learnable in the presence of ELI-ontologies.
no code implementations • 8 Jan 2021 • Cristina Feier, Carsten Lutz, Marcin Przybyłko
We study the complexity of answer counting for ontology-mediated queries and for querying under constraints, considering conjunctive queries and unions thereof (UCQs) as the query language and guarded TGDs as the ontology and constraint language, respectively.
Databases
no code implementations • 19 Nov 2020 • Jean Christoph Jung, Carsten Lutz, Mauricio Martel, Thomas Schneider
We investigate the decidability and computational complexity of conservative extensions and the related notions of inseparability and entailment in Horn description logics (DLs) with inverse roles.
no code implementations • 19 Nov 2020 • Meghyn Bienvenu, Peter Hansen, Carsten Lutz, Frank Wolter
We study FO-rewritability of conjunctive queries in the presence of ontologies formulated in a description logic between EL and Horn-SHIF, along with related query containment problems.
no code implementations • 18 Nov 2020 • Pablo Barcelo, Gerald Berger, Carsten Lutz, Andreas Pieris
In both approaches, we provide semantic characterizations of FO-rewritability that are of independent interest.
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.
no code implementations • 22 Oct 2020 • Cristina Feier, Carsten Lutz, Frank Wolter
We consider ontology-mediated queries (OMQs) based on expressive description logics of the ALC family and (unions) of conjunctive queries, studying the rewritability into OMQs based on instance queries (IQs).
no code implementations • 22 Oct 2020 • Pierre Bourhis, Carsten Lutz
We prove 2NEXPTIME-completeness and extend this result to monadic disjunctive Datalog and to OMQs.
no code implementations • 6 Jul 2020 • Jean Christoph Jung, Carsten Lutz, Hadrien Pulcini, Frank Wolter
We study the separation of positive and negative data examples in terms of description logic (DL) concepts and formulas of decidable FO fragments, in the presence of an ontology.
no code implementations • 3 Jul 2020 • Jean Christoph Jung, Carsten Lutz, Hadrien Pulcini, Frank Wolter
Finding a logical formula that separates positive and negative examples given in the form of labeled data items is fundamental in applications such as concept learning, reverse engineering of database queries, generating referring expressions, and entity comparison in knowledge graphs.
no code implementations • 17 Mar 2020 • Pablo Barcelo, Cristina Feier, Carsten Lutz, Andreas Pieris
We further study the complexity of the meta problem of deciding whether a given OMQ is equivalent to an OMQ of bounded tree width, providing several completeness results that range from NP to 2ExpTime, depending on the DL used.
no code implementations • 21 Jan 2020 • Anneke Haga, Carsten Lutz, Johannes Marti, Frank Wolter
We study complete approximations of an ontology formulated in a non-Horn description logic (DL) such as $\mathcal{ALC}$ in a Horn DL such as~$\mathcal{EL}$.
no code implementations • 28 Dec 2019 • Pablo Barcelo, Victor Dalmau, Cristina Feier, Carsten Lutz, Andreas Pieris
For querying in the presence of constraints, we consider classes of constraint-query specifications (CQSs) that bundle a set of constraints with an actual query.
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).
no code implementations • 31 Jan 2019 • Elena Botoeva, Carsten Lutz, Vladislav Ryzhikov, Frank Wolter, Michael Zakharyaschev
We also consider the problem whether two ALC TBoxes give the same answers to any query over any ABox in a given signature and show that, for CQs, this problem is undecidable, too.
no code implementations • 20 Apr 2018 • Elena Botoeva, Boris Konev, Carsten Lutz, Vladislav Ryzhikov, Frank Wolter, Michael Zakharyaschev
The question whether an ontology can safely be replaced by another, possibly simpler, one is fundamental for many ontology engineering and maintenance tasks.
no code implementations • 18 Apr 2018 • Peter Hansen, Carsten Lutz
A prominent approach to implementing ontology-mediated queries (OMQs) is to rewrite into a first-order query, which is then executed using a conventional SQL database system.
no code implementations • 18 Apr 2018 • Andre Hernich, Carsten Lutz, Fabio Papacchini, Frank Wolter
an ontology O is considered to be in PTime if all (unions of conjunctive) queries can be evaluated in PTime w. r. t.
no code implementations • 20 Sep 2017 • Boris Konev, Carsten Lutz, Ana Ozaki, Frank Wolter
We study the problem of learning description logic (DL) ontologies in Angluin et al.'s framework of exact learning via queries.
no code implementations • 8 Nov 2016 • Carsten Lutz, Frank Wolter
For the latter DL, we additionally show that it is undecidable whether a given ontology admits PTime query evaluation.
no code implementations • 14 Apr 2016 • Elena Botoeva, Carsten Lutz, Vladislav Ryzhikov, Frank Wolter, Michael Zakharyaschev
We also consider the problem whether two ALC TBoxes give the same answers to any query in a given vocabulary over all ABoxes, and show that for CQs this problem is undecidable, too, but becomes decidable and 2EXPTIME-complete in Horn-ALC, and even EXPTIME-complete in Horn-ALC when restricted to (unions of) rooted CQs.
Logic in Computer Science
no code implementations • 15 Jan 2014 • Piero A. Bonatti, Carsten Lutz, Frank Wolter
As fragments of first-order logic, Description logics (DLs) do not provide nonmonotonic features such as defeasible inheritance and default rules.
no code implementations • 28 Jan 2013 • Meghyn Bienvenu, Balder ten Cate, Carsten Lutz, Frank Wolter
Ontology-based data access is concerned with querying incomplete data sources in the presence of domain-specific knowledge provided by an ontology.