Dario Stein

Postdoctoral Researcher · Radboud University Nijmegen · dario-stein@outlook.com

I am a theoretical computer scientist interested in Probability Theory, the Semantics of Programming Languages and Category Theory. These disciplines come together in the exciting new fields of probabilistic programming and categorical probability, which are promising approaches for building verifiable and explainable AI. I am also interested in causal inference, interactive theorem proving, type theory, functional programming with effects, string diagrams, quantum computation and universal algebra.

Until December 2025 I was a Postdoctoral Researcher at the Interdisciplinary Hub for Security, Privacy and Data Governance (iHub) at Radboud University Nijmegen, and affiliated with the Institute for Computing and Information Sciences (iCIS)

Curriculum Vitae

Here is a short overview of my CV. You can find my full CV here.

Researcher in Theoretical Computer Science

iHub, RU Nijmegen

Postdoctoral Researcher with Bart Jacobs

December 2021 - December 2025

DPhil in Computer Science

University of Oxford

Supervisor: Sam Staton

Thesis: Structural Foundations for Probabilistic Programming Languages

October 2021

MASt in Pure Mathematics

Part III of the Mathematical Tripos, University of Cambridge

Assessor: Peter Johnstone

Essay topic: Locally presentable and accessible categories

July 2017

BSc in Mathematics

University of Hamburg

Supervisor: Bernd Siebert

Thesis: On branched coverings of P¹ and orbits of the Hurwitz action

July 2014

Talks

Jan 2025, Keynote "A Welcome to Causal Probabilistic Programming", LAFI Workshop, Rennes
Nov 2025, "Categorical Approaches to Probability", MPI-SP Bochum
Nov 2025, "Categories of Relations which Compose Independently", University of Ljubljana
Sep 2025, "Categories of Relations which Compose Independently", Aarhus University
May 2025, Topos Institute Colloquium
May 2025, "Independence Structures and Dagger Categories of Relations", DutchCATS, University of Utrecht
Mar 2025, "Interventions and Counterfactuals for the Working Programmer", Logic and Semantics Seminar, University of Cambridge
Sep 2024, ItaCa Fest 2024, Online
Jul 2024, SWS Seminar, Radboud University Nijmegen
Jun 2024, DutchCATS 2024, Leiden
Apr 2024, FoSSaCS 2024, Luxembourg
Nov 2023, DutchCATS 2023, Radboud University Nijmegen
Jul 2023, ACT 2023, University of Maryland
Jun 2023, MFPS 2023, Bloomington, Indiana
Jun 2023, CALCO 2023, Bloomington, Indiana (Best Presentation Award)
May 2023, Southern Logic Seminar, UCL
Feb 2023, CSL 2023, University of Warsaw
Jan 2023, Inn'formal Probability Seminar, Universität Innsbruck
Aug 2022, Introduction to Probabilistic Programming, SWS Seminar, Radboud University Nijmegen
Jul 2022, "A Hypergraph Category for Exact Gaussian Inference", Applied Category Theory 22 (slides, video), Strathclyde
Jul 2022, Tutorial on Probabilistic Programming, iHub, Radboud University Nijmegen
Jul 2021, Mathematical Foundations Seminar, Bath
Jul 2021, VeriProP 2021
Jun 2021, LICS 2021
Jan 2021, Oxford Quantum Group Workshop
Jan 2021, POPL 2021 (View on Clowdr)
Jan 2021, LAFI. Slides
Oct 2020, ProbProg workshop, MIT/Online
Feb 2020, PIHOC workshop, IRIF, Paris. Slides
Jan 2020, LAFI workshop, POPL, New Orleans. Slides
2019, Junior Semantics Seminar x 2, Oxford
Jul 2018, ICALP 2018, Prague
2018, Quantum Lunch, Quantum Group, Oxford

Publications

Conference Papers

Graphical Quadratic Algebra
Dario Stein, Fabio Zanasi, Robin Piedeleu, Richard Samuelson
22nd International Colloquium on Theoretical Aspects of Computing (ICTAC 2025), Best Paper Award

Compositional Inference for Bayesian Networks and Causality
Bart Jacobs, Márk Széles and Dario Stein
41st Conference on Mathematical Foundations of Programming Semantics (MFPS 2025)

Random Variables, Conditional Independence and Categories of Abstract Sample Spaces
Dario Stein
40th Annual ACM/IEEE Symposium on Logic in Computer Science (LICS 2025)

Combs, Causality and Contractions in Atomic Markov Categories
Dario Stein, Márk Széles
Electronic Proceedings in Theoretical Computer Science (ACT 2024)

Towards a Compositional Framework for Convex Analysis (with Applications to Probability Theory)
Dario Stein, Richard Samuelson
Foundations of Software Science and Computation Structures: 27th International Conference (FoSSaCS 2024)

Overdrawing Urns using Categories of Signed Probabilities
Bart Jacobs, Dario Stein
Electronic Proceedings in Theoretical Computer Science 397 (ACT 2023)

Pearl's and Jeffrey's Update as Modes of Learning in Probabilistic Programming
Bart Jacobs, Dario Stein
Electronic Notes in Theoretical Informatics and Computer Science, Volume 3 (MFPS 2023)

A Category for unifying Gaussian Probability and Nondeterminism
Dario Stein, Richard Samuelson
10th Conference on Algebra and Coalgebra in Computer Science (CALCO 2023)

Counting and Matching
Bart Jacobs, Dario Stein
31st EACSL Annual Conference on Computer Science Logic (CSL 2023)

Compositional Semantics for Probabilistic Programs with Exact Conditioning
Dario Stein, Sam Staton
Proceedings of the 36th Annual ACM/IEEE Symposium on Logic in Computer Science (LICS 2021) Distinguished Paper Award

Probabilistic Programming Semantics for Name Generation
Marcin Sabok, Sam Staton, Dario Stein, Michael Wolman
Proceedings of the ACM on Programming Languages, Volume 5 (POPL 2021)

The Beta-Bernoulli process and Algebraic Effects
Sam Staton, Dario Stein, Hongseok Yang, Nathanael L. Ackerman, Cameron E. Freer, Daniel M. Roy.
45th International Colloquium on Automata, Languages, and Programming (ICALP 2018)

Journal Articles

A Categorical Treatment of Open Linear Systems
Dario Stein, Richard Samuelson
Logical Methods in Computer Science, CALCO 2023 Special Issue Invited Article

Dilations and information flow axioms in categorical probability
Tobias Fritz, Tomáš Gonda, Nicholas Gauguin Houghton-Larsen, Paolo Perrone, Dario Stein
Mathematical Structures in Computer Science , Volume 33 , Issue 10 (2023)

Probabilistic Programming with Exact Conditions
Dario Stein, Sam Staton
Journal of the ACM, Volume 71, Issue 1 (2023) Invited Article

DPhil Thesis

Structural Foundations for Probabilistic Programming Languages
Dario Stein
DPhil Thesis, University of Oxford, 2021

Preprints

Dagger categories of relations: the equivalence of dilatory dagger categories and epi-regular independence categories
Matthew Di Meglio, Chris Heunen, Jean-Simon Pacaud Lemay, Paolo Perrone, Dario Stein

Absolute continuity, supports and idempotent splitting in categorical probability
Tobias Fritz, Tomáš Gonda, Antonio Lorenzin, Paolo Perrone, Dario Stein

Prospective Students

Are you a motivated student looking for a project? Write me an email! I am keen on (co)supervising BSc and MSc Projects as well as Research Internships. Below are some example topics that interest me:

BSc Topics

Presentations of Convex Spaces
Convex spaces are algebraic structures similar to vector spaces, which model convex subsets of Euclidean space. They are useful in the study of probabilistic computation. You will investigate some algebraic questions about convex spaces, related to free algebras and presentations.

Reflections into Free Algebras
Free algebras are the basic building blocks of algebraic structures. You will investigate algebras which can be approximated by free algebras in a certain sense, or prove why such an approximation is impossible.

Uniqueness of Retrodiction:
You will study the monoid of endo-relations on a set X, and try to classify the automorphisms of this monoid.

MSc Topics

Nominal Sets and Probability
Nominal sets are a mathematical formalism for dealing with names such as variable names or memory locations in programming languages. It doesn't matter what these names are -- we only care whether two names are equal or not. For example, variables bindings are often considered up to α-equivalence. In this project, you'll investigate various formal similarities between fresh name generation (choosing a new variable name, or allocating a memory location), and probability.

Random Variables and Isometry-Sets
How can the notion of random variables be formalized in category theory? This project will involve sheaves over categories of sample spaces. A concrete model are Iso-Sets, a novel continuous generalization of nominal sets using isometries of Euclidean space

Type Theory for Equivariance
Group actions are a fundamental language for describing mathematical structures with symmetries. How would a type theory look where everything that typechecks is automatically equivariant?

Formalization of Categorical Probability
There are many challenges involving monoidal category theory and string diagrams in proof assistants such as Lean or Rocq

Supervision

PhD Students
Márk Széles (cosupervision with Bart Jacobs), 2023 - present

Bachelor Students
Gideon de Hoop (daily supervisor), Sep 2024-Jan 2025

MFOCS Seminar
Tjitske Koster (2022), Sergio Dominguez Cabrera (2023), Dick Blankvoort (2023), Bas van der Linden (2024)

Teaching

Spring 25, Lecturer for Category Theory and Coalgebra, Radboud University Nijmegen
Spring 24, Lecturer for Category Theory and Coalgebra, Radboud University Nijmegen
Winter 2023-24, MFoCS Seminar at Radboud University Nijmegen
Spring 23, Lecturer for Category Theory and Coalgebra, Radboud University Nijmegen
Winter 2022-23, MFoCS Seminar at Radboud University Nijmegen
Spring 2022, Tutor for Category Theory and Coalgebra at Radboud University Nijmegen
Michaelmas 2020, Tutor for Categories, Proofs and Processes at University of Oxford
Hilary 2020, Tutor for Quantum Information at University of Oxford
Michaelmas 2019, Tutor for Principles of Programming Languages at University of Oxford.
Hilary 2019, Tutor for Probability and Computing at University of Oxford.

Service

Program Committees

Committee Member for 41st Conference on Mathematical Foundations of Programming Semantics (MFPS 2025)
Committee Member for Applied Category Theory (ACT 2024)
Committee Member for Applied Category Theory (ACT 2023)
Committee Member for Languages for Inference (LAFI 2023)
Committee Member for ProbProg 2021

Reviewer

29th International Conference on Foundations of Software Science and Computation Structures (FoSSaCS 2026)
34th EACSL Annual Conference on Computer Science Logic (CSL 2026)
53rd ACM SIGPLAN Symposium on Principles of Programming Languages (POPL 2026)
Compositionality (2025)
Proceedings of the Royal Society (2025)
Annals of Pure and Applied Logic (2024)
Compositionality (2024)
39th Annual Symposium on Logic in Computer Science (LICS 2024)
27th International Conference on Foundations of Software Science and Computation Structures (FoSSaCS 2024)
32nd European Symposium on Programming (ESOP 2023)
26th International Conference on Foundations of Software Science and Computation Structures (FoSSaCS 2023)
47th International Symposium on Mathematical Foundations of Computer Science (MFCS 2022)
37th Annual Symposium on Logic in Computer Science (LICS 2022)
36th Annual Symposium on Logic in Computer Science (LICS 2021)
International Conference on Formal Structures for Computation and Deduction (FSCD)
Mathematical Structures in Computer Science (MSCS)

Student Volunteer

47th ACM SIGPLAN Symposium on Principles of Programming Languages (POPL 2020)
Federated Logic Conference (FLOC 2018)

Contact Information

Email: dario.stein@ru.nl

Office: Room 19.28, Erasmus Building, Erasmusplein 1, 6525 HT Nijmegen, The Netherlands