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- articleJanuary 2024
How to Tell Easy from Hard: Complexities of Conjunctive Query Entailment in Extensions of ALC
Journal of Artificial Intelligence Research (JAIR), Volume 78Pages 385–458https://doi.org/10.1613/jair.1.14482It is commonly known that the conjunctive query entailment problem for certain extensions of (the well-known ontology language) ALC is computationally harder than their knowledge base satisfiability problem while for others the complexities coincide, both ...
- research-articleAugust 2023
Tractable diversity: scalable multiperspective ontology management via standpoint EL
IJCAI '23: Proceedings of the Thirty-Second International Joint Conference on Artificial IntelligenceArticle No.: 363, Pages 3258–3267https://doi.org/10.24963/ijcai.2023/363The tractability of the lightweight description logic EL has allowed for the construction of large and widely used ontologies that support semantic interoperability. However, comprehensive domains with a broad user base are often at odds with strong ...
- research-articleJune 2023
Bounded Treewidth and the Infinite Core Chase: Complications and Workarounds toward Decidable Querying
PODS '23: Proceedings of the 42nd ACM SIGMOD-SIGACT-SIGAI Symposium on Principles of Database SystemsPages 291–302https://doi.org/10.1145/3584372.3588659The core chase, a popular algorithm for answering conjunctive queries (CQs) over existential rules, is guaranteed to terminate and compute a finite universal model whenever one exists, leading to the equivalence of the universal-model-based and the chase-...
- ArticleSeptember 2022
Semantic Characterizations of AGM Revision for Tarskian Logics
AbstractGiven the increasingly dynamic nature of knowledge in the era of Web-based information exchange, techniques to revise recorded knowledge – such as knowledge graphs or ontologies – with respect to new findings are more important than ever. For ...
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- research-articleJune 2022
A Journey to the Frontiers of Query Rewritability
PODS '22: Proceedings of the 41st ACM SIGMOD-SIGACT-SIGAI Symposium on Principles of Database SystemsPages 359–367https://doi.org/10.1145/3517804.3524163We consider (first-order) query rewritability in the context of theory-mediated query answering. The starting point of our journey is the FUS/FES conjecture, which states that any theory that is a finite expansion set (FES) and admits query rewriting (...
- chapterMarch 2022
Explaining Data with Formal Concept Analysis
Reasoning Web. Explainable Artificial IntelligencePages 153–195https://doi.org/10.1007/978-3-030-31423-1_5AbstractWe give a brief introduction into Formal Concept Analysis, an approach to explaining data by means of lattice theory.
- research-articleNovember 2021
Finite model theory of the triguarded fragment and related logics
LICS '21: Proceedings of the 36th Annual ACM/IEEE Symposium on Logic in Computer ScienceArticle No.: 34, Pages 1–13https://doi.org/10.1109/LICS52264.2021.9470734The Triguarded Fragment (TGF) is among the most expressive decidable fragments of first-order logic, subsuming both its two-variable and guarded fragments without equality. We show that the TGF has the finite model property (providing a tight doubly ...
- articleMay 2021
On the Decomposition of Abstract Dialectical Frameworks and the Complexity of Naive-based Semantics
Journal of Artificial Intelligence Research (JAIR), Volume 70Pages 1–64https://doi.org/10.1613/jair.1.11348Abstract dialectical frameworks (ADFs) are a recently introduced powerful generalization of Dung’s popular abstract argumentation frameworks (AFs). Inspired by similar work for AFs, we introduce a decomposition scheme for ADFs, which proceeds along the ...
- research-articleJanuary 2020
Completeness and soundness guarantees for conjunctive SPARQL queries over RDF data sources with completeness statements1
RDF generally follows the open-world assumption: information is incomplete by default. Consequently, SPARQL queries cannot retrieve with certainty complete answers, and even worse, when they involve negation, it is unclear whether they produce sound ...
- ArticleAugust 2019
Worst-case optimal querying of very expressive description logics with path expressions and succinct counting
IJCAI'19: Proceedings of the 28th International Joint Conference on Artificial IntelligencePages 1530–1536Among the most expressive knowledge representation formalisms are the description logics of the Ƶ family. For well-behaved fragments of ƵOIQ, entailment of positive two-way regular path queries is well known to be 2EXPTIME-complete under the proviso of ...
- ArticleSeptember 2017
Not Too Big, Not Too Small... Complexities of Fixed-Domain Reasoning in First-Order and Description Logics
AbstractWe consider reasoning problems in description logics and variants of first-order logic under the fixed-domain semantics, where the model size is finite and explicitly given. It follows from previous results that standard reasoning is NP-complete ...
- ArticleAugust 2016
Fixed-domain reasoning for description logics
ECAI'16: Proceedings of the Twenty-second European Conference on Artificial IntelligencePages 819–827https://doi.org/10.3233/978-1-61499-672-9-819After decades of fruitful research, description logics (DLs) have evolved into a de facto standard in logic-based knowledge representation. In particular, they serve as the formal basis of the standardized and very popular web ontology language (OWL), ...
- ArticleJuly 2016
Expressivity of datalog variants: completing the picture
IJCAI'16: Proceedings of the Twenty-Fifth International Joint Conference on Artificial IntelligencePages 1230–1236Computational and model-theoretic properties of logical languages constitute a central field of research in logic-based knowledge representation. Datalog is a very popular formalism, a de-facto standard for expressing and querying knowledge. Diverse ...
- ArticleJuly 2015
Characterization of the expressivity of existential rule queries
IJCAI'15: Proceedings of the 24th International Conference on Artificial IntelligencePages 3193–3199Existential rules (also known as Datalog± or tuple-generating dependencies) have been intensively studied in recent years as a prominent formalism in knowledge representation and database systems. We consider them here as a querying formalism, extending ...
- ArticleJuly 2015
On the computational complexity of naive-based semantics for abstract dialectical frameworks
IJCAI'15: Proceedings of the 24th International Conference on Artificial IntelligencePages 2985–2991Abstract dialectical frameworks (ADFs) are a powerful generalization of Dung's abstract argumentation frameworks. ADFs allow to model argumentation scenarios such that ADF semantics then provide interpretations of the scenarios. Among the considerable ...
- ArticleJuly 2015
Reasonable highly expressive query languages
IJCAI'15: Proceedings of the 24th International Conference on Artificial IntelligencePages 2826–2832Expressive query languages are gaining relevance in knowledge representation (KR), and new reasoning problems come to the fore. Especially query containment is interesting in this context. The problem is known to be decidable for many expressive query ...
- ArticleOctober 2014
Towards combining machine learning with attribute exploration for ontology refinement
ISWC-PD'14: Proceedings of the 2014 International Conference on Posters & Demonstrations Track - Volume 1272Pages 229–232We propose a new method for knowledge acquisition and ontology refinement for the Semantic Web utilizing Linked Data available through remote SPARQL endpoints. This method is based on combination of the attribute exploration algorithm from formal ...
- articleOctober 2014
(Non-)Succinctness of uniform interpolants of general terminologies in the description logic EL
Artificial Intelligence (ARTI), Volume 215, Issue 1Pages 120–140https://doi.org/10.1016/j.artint.2014.06.005EL is a popular description logic, used as a core formalism in large existing knowledge bases. Uniform interpolants of knowledge bases are of high interest, e.g. in scenarios where a knowledge base is supposed to be partially reused. However, to the ...
- articleSeptember 2014
The complexity of answering conjunctive and navigational queries over OWL 2 EL knowledge bases
OWL 2 EL is a popular ontology language that supports role inclusions--axioms of the form S1...Sn ⊆ S that capture compositional properties of roles. Role inclusions closely correspond to context-free grammars, which was used to show that answering ...