I did mathematics.
Now I’m trying to find out if I produced something useful.
I'm Reijo Jaakkola, a mathematician. My background is in logic, machine learning and theoretical computer science. My future is in business.
Current focus
ExplainedAI
ExplainedAI is a Research-to-Business project where we are preparing the commercialization of new interpretable machine learning solutions. Funded by Business Finland and Tampere University.
Research areas
Four things I have thought about
Mathematical logic
Formal tools for understanding structure, expressivity, and computation.
Machine learning
What models actually learn, when they generalize, and why.
Explainable AI
Methods for making machine learning models and predictions more understandable.
Complexity theory
What can be computed, how fast, and where the hard cases hide.
Selected publications
What I've written
- Why this and not that? A Logic-based Framework for Contrastive Explanations Publication Preprint
- Explainability via Short Formulas: the Case of Propositional Logic with Implementation Publication
- Relating Description Complexity to Entropy Publication
- Description Complexity of Unary Structures in First-Order Logic with Links to Entropy Publication Preprint
- Interpretable Classifiers for Tabular Data via Feature Selection and Discretization Publication Preprint
- Short Boolean Formulas as Explanations in Practice Publication Preprint
- Relating Description Complexity to Entropy Publication Preprint
- Complexity of Polyadic Boolean Modal Logics: Model Checking and Satisfiability Publication Preprint
- Complexity Classifications via Algebraic Logic Publication Preprint
- Explainability via Short Formulas: the Case of Propositional Logic with Implementation Publication Preprint
- Towards Model Theory of Ordered Logics: Expressivity and Interpolation Publication Preprint
- Uniform Guarded Fragments Publication Preprint
- Ordered Fragments of First-Order Logic Publication Preprint
- A monotone connection between model class size and description length Preprint
- Convergence in the space of compact labeled metric spaces Preprint
- First-order logic with self-reference Preprint
- An Extension of Trakhtenbrot's Theorem Note
- Complexity of the Ackermann fragment with one leading existential quantifier Note
Selected talks
Where I've spoken
- Moderni selitettävä tekoäly Slides
- Why this and not that? A Logic-based Framework for Contrastive Explanations Slides
- Description Complexity of Unary Structures in First-Order Logic with Links to Entropy Slides
- Expressing boundedness in static computational logic Slides
- Description complexity Slides
- Uniform guarded fragments: interpolation and complexity Slides
- Formulas of propositional logic as interpretable classifiers Slides
- Why do overparameterized neural networks generalize? Slides
- Explaining Classifiers and Data via Propositional Logic Slides
- First-Order Logic with Game-Theoretic Recursion Slides
- The Asymptotic Equipartition Property
- Relating Description Complexity to Entropy Slides
- First-Order Logic with Game-Theoretic Recursion Slides
- Complexity of Polyadic Boolean Modal Logics Slides
- Complexity Classifications via Algebraic Logic Slides
- First order logic with game-theoretic recursion II
- Nopeat algoritmit ja laskennallinen vaativuusteoria (invited) Slides (FI)
- First-order logic with self-reference Slides
- Uniform Guarded Fragments Slides
- Complexity of Polyadic Boolean Modal Logics
- Undecidability of the Halting Problem and Gödel's Incompleteness Theorems Slides Video
- Ordered fragments of first-order logic Slides
- What is a fragment? Slides
- Interpolation and fragments of first-order logic
- Ordered fragments of first-order logic Slides
- Extensions of two-variable logic Slides
- Algebraic classifications for fragments of first-order logic and beyond Slides
More
Awards, theses, activities
Awards
- First Prize — Amplifying Financial AI with Quantum Data Augmentation. Hanken Quantum × AI Hackathon 2025. Website
- Best Tech Solution — Unlocking ESG Insights. Hanken Quantum Hackathon 2023. Website
- 2022 Ernst Lindelöf Prize. Best master's thesis in mathematics in Finland, 2021–2022.
Theses
- Algebraic Fragments of First-Order Logic. Master's thesis, Tampere University, 2021. Thesis
Activities
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Research visits
- TU Wien — host: Mantas Šimkus — interpretable graph classifiers — 14–18 July 2025
- TU Wien — host: Magdalena Ortiz — knowledge graphs & neural networks — 16–20 December 2024
- TU Wien — host: Thomas Eiter — explaining AI via logic — 27 November – 1 December 2023
- University of Wrocław & TU Dresden — host: Bartosz Bednarczyk — model theory of ordered fragments — 10–23 March 2023
- Organized a Young Researchers session at the Finnish Mathematical Days 2024.
- Reviewer for AAMAS 2022, IJCAI 2023, KR 2023, MFCS 2023, JELIA 2023, GandALF 2023, AAAI 2024, LICS 2024, KR 2024, AAMAS 2025, KR 2025, GandALF 2025, STACS 2026, and the journals LMCS and JLC.
Quotes I keep around
But what we can't say we can't say, and we can't whistle it either. Frank Ramsey
Young man, in mathematics you don't understand things. You just get used to them. John von Neumann
Bad ideas is good, good ideas is terrific, no ideas is terrible. Leonard E. Baum
Everybody who has worked in formal logic will confirm that it is one of the technically most refractory parts of mathematics. John von Neumann
Contact
Get in touch
- reijo.jaakkola@tuni.fi
- /in/reijo-jaakkola
- GitHub
- @ReijoJaakkola
- Scholar
- Google Scholar
- CSTheory
- cstheory.stackexchange.com