Asta (formerly Andreas) Halkjær
From
I am a PhD student at DTU Compute since February 2020 working on Formally Correct Deduction Methods for Computational Logic, especially using the proof assistant Isabelle/HOL. My supervisor is Jørgen Villadsen and my co-supervisor is Nina Gierasimczuk.
I was a MSc student on the Honours Programme in Computer Science and Engineering at DTU from 2018 to 2020. My MSc thesis on Hybrid Logic was supervised by Jørgen Villadsen, Alexander Birch Jensen and Patrick Blackburn.
Articles
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Isabelle/HOL as a Meta-Language for Teaching Logic in
ThEdu'20 post-proceedings
Asta Halkjær From, Jørgen Villadsen, Patrick Blackburn.
DOI: 10.4204/EPTCS.328.2
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Hybrid Logic in the Isabelle Proof Assistant: Benefits, Challenges and the Road
Ahead at AiML 2020
Asta Halkjær From
Booklet: PDF
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Formalizing Henkin-Style Completeness of an Axiomatic System for Propositional
Logic
at WeSSLLII + ESSLLI Virtual Student Session 2020 Asta Halkjær FromProceedings: PDF
- A Concise Sequent Calculus for Teaching First-Order Logic at Isabelle Workshop 2020 Asta Halkjær From, Jørgen Villadsen.
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Formalizing a Seligman-Style Tableau System for Hybrid Logic (short paper) at
IJCAR 2020
Asta Halkjær From, Patrick Blackburn, Jørgen Villadsen.
DOI: 10.1007/978-3-030-51074-9_27
Talk: YouTube -
Teaching a Formalized Logical Calculus in
ThEdu'19 post-proceedings
Asta Halkjær From, Alexander Birch Jensen, Anders Schlichtkrull, Jørgen Villadsen.
DOI: 10.4204/EPTCS.313.5
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Multi-Agent Programming Contest 2018 -
The Jason-DTU Team
Jørgen Villadsen, Mads Okholm Bjørn, Andreas Halkjær From, Thomas Søren Henney, John
Bruntse Larsen.
Lecture Notes in Computer Science, vol 11957, pp. 41-71. Springer.
Editors: Tobias Ahlbrecht, Jürgen Dix and Niklas Fiekas. - A Verified Simple Prover for First-Order Logic at PAAR 2018 Jørgen Villadsen, Anders Schlichtkrull, Andreas Halkjær From.
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Students' Proof Assistant (SPA) in
ThEdu'18 post-proceedings
Anders Schlichtkrull, Jørgen Villadsen, Andreas Halkjær From.
DOI: 10.4204/EPTCS.290.1
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Natural Deduction Assistant (NaDeA) in
ThEdu'18 post-proceedings
Jørgen Villadsen, Andreas Halkjær From, Anders Schlichtkrull.
DOI: 10.4204/EPTCS.290.2
- Substitutionless First-Order Logic: A Formal Soundness Proof at Isabelle Workshop 2018 Andreas Halkjær From, John Bruntse Larsen, Anders Schlichtkrull, Jørgen Villadsen.
- Drawing Trees at Isabelle Workshop 2018 Andreas Halkjær From, Anders Schlichtkrull, Jørgen Villadsen.
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Natural Deduction and the Isabelle Proof Assistant in
ThEdu'17 post-proceedings
Jørgen Villadsen, Andreas Halkjær From, Anders Schlichtkrull.
Includes my work on translating online NaDeA proofs to the Isabelle encoding of the proof system.
DOI: 10.4204/EPTCS.267.9
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Multi-Agent Programming Contest 2016 - The Python-DTU Team in
IJAOSE
2018
Jørgen Villadsen, Andreas Halkjær From, Salvador Jacobi, Nikolaj Nøkkentved Larsen.
I did the initial work on the code used by the Python-DTU team for the Multi-Agent Programming Contest 2016.
- Code Generation for a Simple First-Order Prover at Isabelle Workshop 2016 Jørgen Villadsen, Anders Schlichtkrull, Andreas Halkjær From.
Published formalizations
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Hybrid Logic in
Archive of Formal Proofs (December 2019)
Asta Halkjær From
The formalization accompanying my MSc thesis.
The development version contains the latest results. -
A Sequent Calculus for First-Order Logic in
Archive of Formal Proofs (July 2019)
Andreas Halkjær From
This work formalizes soundness and completeness of a one-sided sequent calculus for first-order logic. The completeness is shown via a translation from a complete semantic tableau calculus, the proof of which is based on the First-Order Logic According to Fitting theory. The calculi and proof techniques are taken from Ben-Ari's Mathematical Logic for Computer Science.
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Epistemic Logic in
Archive of Formal Proofs (October 2018)
Andreas Halkjær From
This work is a formalization of epistemic logic with countably many agents. It includes proofs of soundness and completeness for the axiom system K. The completeness proof is based on the textbook "Reasoning About Knowledge" by Fagin, Halpern, Moses and Vardi (MIT Press 1995).
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IsaFoL: Isabelle Formalization of Logic
I have contributed to a number of formalizations in the IsaFoL project:
Abstracts
Theses
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MSc: Hybrid Logic (January 2020)
My MSc thesis on formalizing the soundness and completeness of a Seligman-style tableau system for hybrid logic in Isabelle/HOL.
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BSc: Formalized First-Order Logic (July 2017)
My BSc thesis on formalizing the soundness and completeness of NaDeA in Isabelle/HOL.
Talks
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Hybrid Logic (January 2021)
Given at 3rd World Logic Day - 14 January 2021 - A Zoom on Logic.
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Belief Revision and Isabelle/HOL (November 2020)
Given at a DTU seminar course.
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Hybrid Logic in the Isabelle Proof Assistant: Benefits, Challenges and the Road Ahead
Given at AiML 2020.
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Formally Correct Deduction Methods for Computational Logic (July 2020)
Given at CICM 2020 doctoral session.
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Formalizing Henkin-Style Completeness of an Axiomatic System for Propositional Logic (July 2020)
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Formalizing a Seligman-Style Tableau System for Hybrid Logic (July 2020)
Overview of our paper. Recording: YouTube. Given at IJCAR 2020.
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A Concise Sequent Calculus for Teaching First-Order Logic (June 2020)
Overview of our paper. Recording: YouTube. Given at the Isabelle Workshop 2020.
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The Isabelle Proof Assistant and Hybrid Logic: Formalizing Seligman-Style Tableaux (October 2019)
Update on my MSc thesis work. Given at an AlgoLoG seminar at DTU.
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Using the Isabelle Proof Assistant: Seligman-Style Tableau for Hybrid Logic (September 2019)
The Isabelle proof assistant can be used to mechanically develop and check results in logic, mathematics, computer science etc. In this talk I motivate this process and explain how it looks in practice for a basic hybrid logic. The running example will be preliminary work on the completeness and termination for a Seligman-style tableau system by Blackburn, Bolander, Braüner and Jørgensen. Given at The LogicS of Prior Past, Present, and Future at Roskilde University.
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Magnolia – Implementing System F with Anonymous Sums and Products (March 2018)
Overview of the Complete and Easy Bidirectional Type Checking for Higher-Rank Polymorphism paper as well as my own additions. Also briefly describes Abstract Binding Trees. Given at DTU.
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FIT – From's Isabelle Tutorial – Verification of Quicksort (October 2017)
A fast-paced, hands-on introduction to Isabelle/HOL I gave at PART DTU.
Software
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A Pretty but not Greedy Printer (January 2018)
My implementation of Jean-Philippe Bernardy's A Pretty But Not Greedy Printer (Functional Pearl). PACMPL 1(ICFP): 6:1-6:21 (2017) in OCaml. The author of the paper has a version in Haskell.
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Sudoku Solver (June 2016)
A solver for large Sudoku puzzles which we wrote as a fourth-semester final project. Solving is done either using our own backtracking tactic solver or with an external SAT solver by compiling the problem into the CNF-format DIMACS. The GitHub page includes an abstract in English.
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The Playground (December 2015)
My solution to an internal programming competition in the Algorithms and Data Structures 2 course at DTU. The readme includes a description of the problem and my algorithm as well as fully annotated version of the C code.
GitHub
Work Experience
Teaching Assistant
I am or have been a TA in the following courses:- 02101 Introductory Programming, fall 2015
- 02105 Algorithms and Data Structures 1, spring 2016
- 02101 Introductory Programming, fall 2016
- 02110 Algorithms and Data Structures 2, fall 2016
- 02105 Algorithms and Data Structures 1, spring 2017
- 02180 Introduction to Artificial Intelligence, spring 2018
- 02156 Logical Systems and Logic Programming, fall 2018
- 02156 Logical Systems and Logic Programming, fall 2019
- 02102 Introductory Programming, spring 2020
- 02256 Automated Reasoning, spring 2020
- 02287 Logical Theories for Uncertainty and Learning, fall 2020