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Found 32 papers, 1 papers with code
Towards Ontology Construction with Language Models
We present a method for automatically constructing a concept hierarchy for a given domain by querying a large language model.
Querying Circumscribed Description Logic Knowledge Bases
Circumscription is one of the main approaches for defining non-monotonic description logics (DLs).
Description Logics with Abstraction and Refinement
Ontologies often require knowledge representation on multiple levels of abstraction, but description logics (DLs) are not well-equipped for supporting this.
SAT-Based PAC Learning of Description Logic Concepts
We propose bounded fitting as a scheme for learning description logic concepts in the presence of ontologies.
On the non-efficient PAC learnability of conjunctive queries
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.
Ontology-Mediated Querying on Databases of Bounded Cliquewidth
We study the evaluation of ontology-mediated queries (OMQs) on databases of bounded cliquewidth from the viewpoint of parameterized complexity theory.
Frontiers and Exact Learning of ELI Queries under DL-Lite Ontologies
We study ELI queries (ELIQs) in the presence of ontologies formulated in the description logic DL-Lite.
Conservative Extensions for Existential Rules
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.
How to Approximate Ontology-Mediated Queries
(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.
Actively Learning Concepts and Conjunctive Queries under ELr-Ontologies
We also show that EL-concepts are not polynomial query learnable in the presence of ELI-ontologies.
Answer Counting under Guarded TGDs
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
Conservative Extensions in Horn Description Logics with Inverse Roles
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.
First Order-Rewritability and Containment of Conjunctive Queries in Horn Description Logics
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.
Query Expressibility and Verification in Ontology-Based Data Access
In ontology-based data access, multiple data sources are integrated using an ontology and mappings.
First-Order Rewritability of Frontier-Guarded Ontology-Mediated Queries
In both approaches, we provide semantic characterizations of FO-rewritability that are of independent interest.
From Conjunctive Queries to Instance Queries in Ontology-Mediated Querying
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).
Containment in Monadic Disjunctive Datalog, MMSNP, and Expressive Description Logics
We prove 2NEXPTIME-completeness and extend this result to monadic disjunctive Datalog and to OMQs.
Separating Positive and Negative Data Examples by Concepts and Formulas: The Case of Restricted Signatures
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.
Logical Separability of Labeled Data Examples under Ontologies
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.
When is Ontology-Mediated Querying Efficient?
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.
A Journey into Ontology Approximation: From Non-Horn to Horn
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~$\mathcal{EL}$.
The Limits of Efficiency for Open- and Closed-World Query Evaluation Under Guarded TGDs
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.
A Complete Classification of the Complexity and Rewritability of Ontology-Mediated Queries based on the Description Logic EL
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).
Query Inseparability for ALC Ontologies
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.
Inseparability and Conservative Extensions of Description Logic Ontologies: A Survey
The question whether an ontology can safely be replaced by another, possibly simpler, one is fundamental for many ontology engineering and maintenance tasks.
Computing FO-Rewritings in EL in Practice: from Atomic to Conjunctive Queries
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.
Dichotomies in Ontology-Mediated Querying with the Guarded Fragment
an ontology O is considered to be in PTime if all (unions of conjunctive) queries can be evaluated in PTime w. r. t.
Exact Learning of Lightweight Description Logic Ontologies
We study the problem of learning description logic (DL) ontologies in Angluin et al.'s framework of exact learning via queries.
The Data Complexity of Description Logic Ontologies
For the latter DL, we additionally show that it is undecidable whether a given ontology admits PTime query evaluation.
Query-Based Entailment and Inseparability for ALC Ontologies (Full Version)
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
The Complexity of Circumscription in DLs
As fragments of first-order logic, Description logics (DLs) do not provide nonmonotonic features such as defeasible inheritance and default rules.
Ontology-based Data Access: A Study through Disjunctive Datalog, CSP, and MMSNP
Ontology-based data access is concerned with querying incomplete data sources in the presence of domain-specific knowledge provided by an ontology.
