Asta Halkjær From
I was a PhD student at DTU Compute from February 2020 to February 2023 working on Formally Correct Deduction Methods for Computational Logic, especially using the proof assistant Isabelle/HOL. My supervisor was Jørgen Villadsen and my cosupervisor was Nina Gierasimczuk. My thesis defense is in April 2023.
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.
Academic Activities
 Cochair of the Logic and Computation track for the Student Session @ 32nd European Summer School in Logic, Language and Information (ESSLLI 2021).
Awards
 Distinguished Paper Award awarded to Jannis Limperg and me for our CPP 2023 paper on Aesop for Lean 4.
 DTU Travel Grant awarded to me personally by DTU's executive board, February 2022, in recognition of my academic qualities and merits.
Articles

Aesop: WhiteBox BestFirst Proof Search for Lean at
CPP 2023
Jannis Limperg, Asta Halkjær From.
DOI: 10.1145/3573105.3575671
GitHub: JLimperg/aesop 
A Succinct Formalization of the Completeness of FirstOrder Logic in
TYPES 2021 postproceedings
Asta Halkjær From.
DOI: 10.4230/LIPIcs.TYPES.2021.8
Formalization: FirstOrder Logic 
Verifying a Sequent Calculus Prover for FirstOrder Logic with Functions in
Isabelle/HOL at
ITP 2022
Asta Halkjær From, Frederik Krogsdal Jacobsen.
DOI: 10.4230/LIPIcs.ITP.2022.13
Formalization: Prover for FirstOrder Logic 
On Termination for Hybrid Tableaux at
Isabelle Workshop 2022
Asta Halkjær From.
Paper: PDF

SeCaV: A Sequent Calculus Verifier in Isabelle/HOL in
Proceedings 16th Logical and
Semantic Frameworks with Applications (LSFA 2021)
Asta Halkjær From, Frederik Krogsdal Jacobsen, Jørgen Villadsen.
DOI: 10.4204/EPTCS.357.4

Teaching Intuitionistic and Classical Propositional Logic Using Isabelle in
ThEdu'21 postproceedings
Jørgen Villadsen, Asta Halkjær From, Patrick Blackburn.
DOI: 10.4204/EPTCS.354.6

Interactive Theorem Proving for Logic and Information in
Natural Language Processing
in Artificial Intelligence — NLPinAI 2021
Jørgen Villadsen, Asta Halkjær From, Alexander Birch Jensen, Anders Schlichtkrull.
DOI: 10.1007/9783030901387_2
Formalizations: Epistemic Logic, Public Announcement Logic 
Formalized Soundness and Completeness of Epistemic Logic at
WoLLIC 2021
Asta Halkjær From.
DOI: 10.1007/9783030888534_1
https://www.isaafp.org/entries/Synthetic_Completeness.html Formalization: Epistemic Logic 
A Sequent Calculus for FirstOrder Logic Formalized in Isabelle/HOL at
CILC 2021
Asta Halkjær From, Anders Schlichtkrull, Jørgen Villadsen.
CEURWS: PDF
Formalization: Sequent Calculus  A Case Study in ComputerAssisted Metareasoning at DCAI 2021, Special Session on Computational Linguistics, Information, Reasoning, and AI (CompLingInfoReasAI'21) Asta Halkjær From, Simon Tobias Lund, Jørgen Villadsen.
 Formalizing Axiomatic Systems for Propositional Logic in Isabelle/HOL at Conference on Intelligent Computer Mathematics (CICM 2021) Asta Halkjær From, Agnes Moesgård Eschen, Jørgen Villadsen.
 Teaching Automated Reasoning and Formally Verified Functional Programming in Agda and Isabelle/HOL at 10th International Workshop on Trends in Functional Programming in Education (TFPIE 2021) Asta Halkjær From, Jørgen Villadsen.

Synthetic Completeness for a Terminating SeligmanStyle Tableau System in
TYPES 2020 postproceedings
Asta Halkjær From.
DOI: 10.4230/LIPIcs.TYPES.2020.5
Formalization: Hybrid Logic 
Isabelle/HOL as a MetaLanguage for Teaching Logic in
ThEdu'20 postproceedings
Asta Halkjær From, Jørgen Villadsen, Patrick Blackburn.
DOI: 10.4204/EPTCS.328.2

Hybrid Logic in the Isabelle Proof Assistant: Benefits, Challenges and the Road Ahead
(short paper) at AiML 2020
Asta Halkjær From.
Booklet: PDF
Formalization: Hybrid Logic 
Formalizing HenkinStyle Completeness of an Axiomatic System for Propositional
Logic
at WeSSLLII + ESSLLI Virtual Student Session 2020 Asta Halkjær From.Proceedings: PDF

A Concise Sequent Calculus for Teaching FirstOrder Logic at
Isabelle Workshop 2020
Asta Halkjær From, Jørgen Villadsen.
Paper: PDF

Formalizing a SeligmanStyle Tableau System for Hybrid Logic (short paper) at
IJCAR 2020
Asta Halkjær From, Patrick Blackburn, Jørgen Villadsen.
DOI: 10.1007/9783030510749_27
Formalization: Hybrid Logic 
Teaching a Formalized Logical Calculus in
ThEdu'19 postproceedings
Asta Halkjær From, Alexander Birch Jensen, Anders Schlichtkrull, Jørgen Villadsen.
DOI: 10.4204/EPTCS.313.5
 MultiAgent Programming Contest 2018  The JasonDTU Team Jørgen Villadsen, Mads Okholm Bjørn, A. Halkjær From, Thomas Søren Henney, John Bruntse Larsen.

A Verified Simple Prover for FirstOrder Logic at
PAAR 2018
Jørgen Villadsen, Anders Schlichtkrull, A. Halkjær From.
Paper: PDF

Students' Proof Assistant (SPA) in
ThEdu'18 postproceedings
Anders Schlichtkrull, Jørgen Villadsen, A. Halkjær From.
DOI: 10.4204/EPTCS.290.1

Natural Deduction Assistant (NaDeA) in
ThEdu'18 postproceedings
Jørgen Villadsen, A. Halkjær From, Anders Schlichtkrull.
DOI: 10.4204/EPTCS.290.2

Substitutionless FirstOrder Logic: A Formal Soundness Proof at
Isabelle Workshop 2018
A. Halkjær From, John Bruntse Larsen, Anders Schlichtkrull, Jørgen Villadsen.
Paper: PDF

Drawing Trees at
Isabelle Workshop 2018
A. Halkjær From, Anders Schlichtkrull, Jørgen Villadsen.
Paper: PDF, Formalization: Isabelle theory

Natural Deduction and the Isabelle Proof Assistant in
ThEdu'17 postproceedings
Jørgen Villadsen, A. Halkjær From, Anders Schlichtkrull.
DOI: 10.4204/EPTCS.267.9
 MultiAgent Programming Contest 2016  The PythonDTU Team in IJAOSE 2018 Jørgen Villadsen, A. Halkjær From, Salvador Jacobi, Nikolaj Nøkkentved Larsen.

Code Generation for a Simple FirstOrder Prover at
Isabelle Workshop 2016
Jørgen Villadsen, Anders Schlichtkrull, A. Halkjær From.
Paper: PDF
Published formalizations
 Synthetic Completeness in Archive of Formal Proofs (January 2023) Asta Halkjær From.
 Soundness and Completeness of Implicational Logic in Archive of Formal Proofs (September 2022) Asta Halkjær From, Jørgen Villadsen.
 A Naive Prover for FirstOrder Logic in Archive of Formal Proofs (March 2022) Asta Halkjær From.
 A Sequent Calculus Prover for FirstOrder Logic with Functions in Archive of Formal Proofs (February 2022) Asta Halkjær From, Frederik Krogsdal Jacobsen.
 Soundness and Completeness of an Axiomatic System for FirstOrder Logic in Archive of Formal Proofs (October 2021) Asta Halkjær From.
 Public Announcement Logic in Archive of Formal Proofs (June 2021) Asta Halkjær From.
 Epistemic Logic: Completeness of Modal Logics in Archive of Formal Proofs (October 2018, updated April 2021) Asta Halkjær From.
 Hybrid Logic in Archive of Formal Proofs (December 2019, updated June 2020) Asta Halkjær From.
 A Sequent Calculus for FirstOrder Logic in Archive of Formal Proofs (July 2019) Asta Halkjær From.

IsaFoL: Isabelle Formalization of Logic
I have contributed to a number of formalizations in the IsaFoL project:
Abstracts
 On the Use of Isabelle/HOL for Formalizing New Concise Axiomatic Systems for Classical Propositional Logic at TYPES 2021 Asta Halkjær From and Jørgen Villadsen.
 Formalized Soundness and Completeness of Epistemic Logic at LAMAS & SR 2021 Asta Halkjær From, Alexander Birch Jensen and Jørgen Villadsen.
 Formalized soundness and completeness of natural deduction for firstorder logic at SLS 2018 A. Halkjær From.
 Teaching firstorder logic with the natural deduction assistant (NaDeA) at SLS 2018 A. Halkjær From, Helge Hatteland, Jørgen Villadsen.
Theses

PhD: Formally Correct Deduction Methods for Computational Logic (January 2023)
My PhD thesis.

MSc: Hybrid Logic (January 2020)
My MSc thesis on formalizing the soundness and completeness of a Seligmanstyle tableau system for hybrid logic in Isabelle/HOL.

BSc: Formalized FirstOrder Logic (July 2017)
My BSc thesis on formalizing the soundness and completeness of NaDeA in Isabelle/HOL.
Talks

Generic Epistemic and Public Announcement Logic Completeness Results (September 2022)
Given at a Logic & AI @ AlgoLoG seminar, DTU Compute.

Verifying a Sequent Calculus Prover (August 2022)
Given at the ITP 2022 conference together with Frederik Krogsdal Jacobsen.

On Termination for Hybrid Tableaux (August 2022)
Given at the Isabelle Workshop 2022.

Verifying a Sequent Calculus Prover (July 2022)
Given at the DTU PhD Bazaar together with Frederik Krogsdal Jacobsen.

A Naive Prover for FirstOrder Logic  LSD Seminar (May 2022)
Invited talk at the Languages, Systems, and Data Seminar (Spring 2022).

A Naive Prover for FirstOrder Logic  02256 (April 2022)
Guest talk in the course 02256 Automated Reasoning at the Technical University of Denmark.

Formalized Soundness and Completeness of Epistemic Logic (October 2021)
Given at WoLLIC 2021.

Formalizing Axiomatic Systems for Propositional Logic in Isabelle/HOL (July 2021)
Given at CICM 2021.

Formalized Soundness and Completeness of Epistemic Logic (May 2021)
Given at LAMAS & SR 2021.

Hybrid Logic (January 2021)
Given at 3rd World Logic Day  14 January 2021  A Zoom on Logic.

Belief Revision and Isabelle/HOL (November 2020)
Given at a DTU seminar course.

Hybrid Logic in the Isabelle Proof Assistant: Benefits, Challenges and the Road Ahead
Given at AiML 2020.

Formally Correct Deduction Methods for Computational Logic (July 2020)
Given at CICM 2020 doctoral session.

Formalizing HenkinStyle Completeness of an Axiomatic System for Propositional Logic (July 2020)

Formalizing a SeligmanStyle Tableau System for Hybrid Logic (July 2020)
Overview of our paper. Recording: YouTube. Given at IJCAR 2020.

A Concise Sequent Calculus for Teaching FirstOrder Logic (June 2020)
Overview of our paper. Recording: YouTube. Given at the Isabelle Workshop 2020.

The Isabelle Proof Assistant and Hybrid Logic: Formalizing SeligmanStyle Tableaux (October 2019)
Update on my MSc thesis work. Given at an AlgoLoG seminar at DTU.

Using the Isabelle Proof Assistant: SeligmanStyle 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 Seligmanstyle tableau system by Blackburn, Bolander, Braüner and Jørgensen. Given at The LogicS of Prior Past, Present, and Future at Roskilde University.

Formalized Soundness and Completeness of Natural Deduction for FirstOrder Logic (June 2018)
Given at Scandinavian Logic Symposisum 2018 in Gothenburg.

Formalized Soundness and Completeness of Natural Deduction for FirstOrder Logic (June 2018)
Given at Local Isabelle Workshop 2018 at DTU.

Magnolia – Implementing System F with Anonymous Sums and Products (March 2018)
Overview of the Complete and Easy Bidirectional Type Checking for HigherRank Polymorphism paper as well as my own additions. Also briefly describes Abstract Binding Trees. Given at DTU.

FIT – From's Isabelle Tutorial – Verification of Quicksort (October 2017)
A fastpaced, handson introduction to Isabelle/HOL I gave at PART DTU.
Work Experience
Teaching Assistant
I have been a TA in the following courses: 02287 Logical Theories for Uncertainty and Learning, fall 2020
 02256 Automated Reasoning, spring 2020
 02102 Introductory Programming, spring 2020
 02156 Logical Systems and Logic Programming, fall 2019
 02156 Logical Systems and Logic Programming, fall 2018
 02180 Introduction to Artificial Intelligence, spring 2018
 02105 Algorithms and Data Structures 1, spring 2017
 02110 Algorithms and Data Structures 2, fall 2016
 02101 Introductory Programming, fall 2016
 02105 Algorithms and Data Structures 1, spring 2016
 02101 Introductory Programming, fall 2015