Search Results for author:
Found 19 papers, 0 papers with code
Current and Future Challenges in Knowledge Representation and Reasoning
Knowledge Representation and Reasoning is a central, longstanding, and active area of Artificial Intelligence.
Temporalising Unique Characterisability and Learnability of Ontology-Mediated Queries
Recently, the study of the unique characterisability and learnability of database queries by means of examples has been extended to ontology-mediated queries.
Reverse Engineering of Temporal Queries Mediated by LTL Ontologies
In reverse engineering of database queries, we aim to construct a query from a given set of answers and non-answers; it can then be used to explore the data further or as an explanation of the answers and non-answers.
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.
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.
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).
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.
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~$\mathcal{EL}$.
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.
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 Logical Difference for the Lightweight Description Logic EL
In all three cases, we present polynomial-time algorithms that decide whether two terminologies give the same answers to queries over a given vocabulary and compute a succinct representation of the difference if it is non- empty.
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.
Temporal Description Logic for Ontology-Based Data Access (Extended Version)
Our aim is to investigate ontology-based data access over temporal data with validity time and ontologies capable of temporal conceptual modelling.
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.
