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Documents authored by Vehlken, Fabian


Document
Database Theory in Action
Database Theory in Action: Learning Logical Modelling with Iltis

Authors: Tristan Kneisel, Fabian Vehlken, and Thomas Zeume

Published in: LIPIcs, Volume 365, 29th International Conference on Database Theory (ICDT 2026)


Abstract
Important learning objectives in database education are to learn how to design database schemas and how to write queries to access data stored in a database adhering to a schema. In this article we report on results from [Tristan Kneisel et al., 2025] where this learning objective is addressed for the related educational task of modelling with logical formalisms. Two key steps in logical modelling are to (a) choose a suitable vocabulary, that is, e.g., which first-order symbols to use and with which intended meaning, and then to (b) construct actual formal descriptions, i.e. first-order formulas over the chosen vocabulary. While (b) is addressed by several educational support systems for formal foundations of computer science, (a) is so far not addressed at all - likely because it involves specifying the intended meaning of symbols in natural language. We propose a conceptual framework for educational tasks where students choose a vocabulary and implement it for tasks for designing propositional and first-order vocabularies within the Iltis educational system.

Cite as

Tristan Kneisel, Fabian Vehlken, and Thomas Zeume. Database Theory in Action: Learning Logical Modelling with Iltis. In 29th International Conference on Database Theory (ICDT 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 365, pp. 28:1-28:5, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)


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@InProceedings{kneisel_et_al:LIPIcs.ICDT.2026.28,
  author =	{Kneisel, Tristan and Vehlken, Fabian and Zeume, Thomas},
  title =	{{Database Theory in Action: Learning Logical Modelling with Iltis}},
  booktitle =	{29th International Conference on Database Theory (ICDT 2026)},
  pages =	{28:1--28:5},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-413-0},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{365},
  editor =	{ten Cate, Balder and Funk, Maurice},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2026.28},
  URN =		{urn:nbn:de:0030-drops-256426},
  doi =		{10.4230/LIPIcs.ICDT.2026.28},
  annote =	{Keywords: Educational support systems, Logic, Database theory, Natural language processing}
}
Document
Learning Tree Pattern Transformations

Authors: Daniel Neider, Leif Sabellek, Johannes Schmidt, Fabian Vehlken, and Thomas Zeume

Published in: LIPIcs, Volume 328, 28th International Conference on Database Theory (ICDT 2025)


Abstract
Explaining why and how a tree t structurally differs from another tree t^⋆ is a question that is encountered throughout computer science, including in understanding tree-structured data such as XML or JSON data. In this article, we explore how to learn explanations for structural differences between pairs of trees from sample data: suppose we are given a set {(t₁, t₁^⋆),… , (t_n, t_n^⋆)} of pairs of labelled, ordered trees; is there a small set of rules that explains the structural differences between all pairs (t_i, t_i^⋆)? This raises two research questions: (i) what is a good notion of "rule" in this context?; and (ii) how can sets of rules explaining a data set be learned algorithmically? We explore these questions from the perspective of database theory by (1) introducing a pattern-based specification language for tree transformations; (2) exploring the computational complexity of variants of the above algorithmic problem, e.g. showing NP-hardness for very restricted variants; and (3) discussing how to solve the problem for data from CS education research using SAT solvers.

Cite as

Daniel Neider, Leif Sabellek, Johannes Schmidt, Fabian Vehlken, and Thomas Zeume. Learning Tree Pattern Transformations. In 28th International Conference on Database Theory (ICDT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 328, pp. 24:1-24:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)


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@InProceedings{neider_et_al:LIPIcs.ICDT.2025.24,
  author =	{Neider, Daniel and Sabellek, Leif and Schmidt, Johannes and Vehlken, Fabian and Zeume, Thomas},
  title =	{{Learning Tree Pattern Transformations}},
  booktitle =	{28th International Conference on Database Theory (ICDT 2025)},
  pages =	{24:1--24:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-364-5},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{328},
  editor =	{Roy, Sudeepa and Kara, Ahmet},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2025.24},
  URN =		{urn:nbn:de:0030-drops-229652},
  doi =		{10.4230/LIPIcs.ICDT.2025.24},
  annote =	{Keywords: Tree pattern transformations, learning from positive examples, computational complexity}
}
Document
Specification and Automatic Verification of Computational Reductions

Authors: Julien Grange, Fabian Vehlken, Nils Vortmeier, and Thomas Zeume

Published in: LIPIcs, Volume 306, 49th International Symposium on Mathematical Foundations of Computer Science (MFCS 2024)


Abstract
We are interested in the following validation problem for computational reductions: for algorithmic problems P and P^⋆, is a given candidate reduction indeed a reduction from P to P^⋆? Unsurprisingly, this problem is undecidable even for very restricted classes of reductions. This leads to the question: Is there a natural, expressive class of reductions for which the validation problem can be attacked algorithmically? We answer this question positively by introducing an easy-to-use graphical specification mechanism for computational reductions, called cookbook reductions. We show that cookbook reductions are sufficiently expressive to cover many classical graph reductions and expressive enough so that SAT remains NP-complete (in the presence of a linear order). Surprisingly, the validation problem is decidable for natural and expressive subclasses of cookbook reductions.

Cite as

Julien Grange, Fabian Vehlken, Nils Vortmeier, and Thomas Zeume. Specification and Automatic Verification of Computational Reductions. In 49th International Symposium on Mathematical Foundations of Computer Science (MFCS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 306, pp. 56:1-56:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)


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@InProceedings{grange_et_al:LIPIcs.MFCS.2024.56,
  author =	{Grange, Julien and Vehlken, Fabian and Vortmeier, Nils and Zeume, Thomas},
  title =	{{Specification and Automatic Verification of Computational Reductions}},
  booktitle =	{49th International Symposium on Mathematical Foundations of Computer Science (MFCS 2024)},
  pages =	{56:1--56:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-335-5},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{306},
  editor =	{Kr\'{a}lovi\v{c}, Rastislav and Ku\v{c}era, Anton{\'\i}n},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2024.56},
  URN =		{urn:nbn:de:0030-drops-206122},
  doi =		{10.4230/LIPIcs.MFCS.2024.56},
  annote =	{Keywords: Computational reductions, automatic verification, decidability}
}
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