26 Search Results for "Basold, Henning"

Volume

LIPIcs, Volume 239

27th International Conference on Types for Proofs and Programs (TYPES 2021)

TYPES 2021, June 14-18, 2021, Leiden, The Netherlands (Virtual Conference)

Editors: Henning Basold, Jesper Cockx, and Silvia Ghilezan

Document
DOI: 10.4230/LIPIcs.ITP.2025.8
Abstract, Compositional Consistency: Isabelle/HOL Locales for Completeness à la Fitting

Authors: Asta Halkjær From and Anders Schlichtkrull

Published in: LIPIcs, Volume 352, 16th International Conference on Interactive Theorem Proving (ITP 2025)

Abstract
Smullyan and Fitting have used abstract consistency properties to great effect in unifying meta-theoretical results in logic. In this paper, we generalize these developments with the help of Isabelle/HOL. We use locales to decompose abstract consistency into general parts, and provide the textbook variants as special cases. Users can assemble their own consistency property for a given logic. The compositionality alleviates the absence of dependent types in Isabelle/HOL. We use our development to mechanize completeness of calculi for three logics: (1) first-order logic where we only instantiate universal quantifiers with already occurring terms, (2) second-order logic over general models, and (3) a recently developed strong hybrid logic with propositional quantification.
Cite as

Asta Halkjær From and Anders Schlichtkrull. Abstract, Compositional Consistency: Isabelle/HOL Locales for Completeness à la Fitting. In 16th International Conference on Interactive Theorem Proving (ITP 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 352, pp. 8:1-8:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{from_et_al:LIPIcs.ITP.2025.8,
  author =	{From, Asta Halkj{\ae}r and Schlichtkrull, Anders},
  title =	{{Abstract, Compositional Consistency: Isabelle/HOL Locales for Completeness \`{a} la Fitting}},
  booktitle =	{16th International Conference on Interactive Theorem Proving (ITP 2025)},
  pages =	{8:1--8:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-396-6},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{352},
  editor =	{Forster, Yannick and Keller, Chantal},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2025.8},
  URN =		{urn:nbn:de:0030-drops-246406},
  doi =		{10.4230/LIPIcs.ITP.2025.8},
  annote =	{Keywords: Logic, completeness, abstract consistency property, Isabelle/HOL, locales}
}
Document
DOI: 10.4230/LIPIcs.CALCO.2025.7
A Coinductive Representation of Computable Functions

Authors: Alvin Tang and Dirk Pattinson

Published in: LIPIcs, Volume 342, 11th Conference on Algebra and Coalgebra in Computer Science (CALCO 2025)

Abstract
We investigate a representation of computable functions as total functions over 2^∞, the set of finite and infinite sequences over {0,1}. In this model, infinite sequences are interpreted as non-terminating computations whilst finite sequences represent the sum of their digits. We introduce a new definition principle, function space corecursion, that simultaneously generalises minimisation and primitive recursion. This defines the class of computable corecursive functions that is closed under composition and function space corecursion. We prove computable corecursive functions represent all partial recursive functions, and show that all computable corecursive functions are indeed computable by translation into the untyped λ-calculus.
Cite as

Alvin Tang and Dirk Pattinson. A Coinductive Representation of Computable Functions. In 11th Conference on Algebra and Coalgebra in Computer Science (CALCO 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 342, pp. 7:1-7:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{tang_et_al:LIPIcs.CALCO.2025.7,
  author =	{Tang, Alvin and Pattinson, Dirk},
  title =	{{A Coinductive Representation of Computable Functions}},
  booktitle =	{11th Conference on Algebra and Coalgebra in Computer Science (CALCO 2025)},
  pages =	{7:1--7:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-383-6},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{342},
  editor =	{C\^{i}rstea, Corina and Knapp, Alexander},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CALCO.2025.7},
  URN =		{urn:nbn:de:0030-drops-235662},
  doi =		{10.4230/LIPIcs.CALCO.2025.7},
  annote =	{Keywords: Computability, Coinduction}
}
Document
DOI: 10.4230/LIPIcs.TYPES.2024.5
Implementing a Type Theory with Observational Equality, Using Normalisation by Evaluation

Authors: Matthew Sirman, Meven Lennon-Bertrand, and Neel Krishnaswami

Published in: LIPIcs, Volume 336, 30th International Conference on Types for Proofs and Programs (TYPES 2024)

Abstract
We report on an experimental implementation in Haskell of a dependent type theory featuring an observational equality type, based on Pujet et al.’s CCobs. We use normalisation by evaluation to produce an efficient normalisation function, which is used to implement a bidirectional type checker. To allow for greater expressivity, we extend the core CCobs calculus with quotient types and inductive types. To make the system usable, we explore various proof-assistant features, notably a rudimentary version of a "hole" system similar to Agda’s. While rather crude, this experience should inform other, more substantial implementation efforts of observational equality.
Cite as

Matthew Sirman, Meven Lennon-Bertrand, and Neel Krishnaswami. Implementing a Type Theory with Observational Equality, Using Normalisation by Evaluation. In 30th International Conference on Types for Proofs and Programs (TYPES 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 336, pp. 5:1-5:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{sirman_et_al:LIPIcs.TYPES.2024.5,
  author =	{Sirman, Matthew and Lennon-Bertrand, Meven and Krishnaswami, Neel},
  title =	{{Implementing a Type Theory with Observational Equality, Using Normalisation by Evaluation}},
  booktitle =	{30th International Conference on Types for Proofs and Programs (TYPES 2024)},
  pages =	{5:1--5:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-376-8},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{336},
  editor =	{M{\o}gelberg, Rasmus Ejlers and van den Berg, Benno},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TYPES.2024.5},
  URN =		{urn:nbn:de:0030-drops-233673},
  doi =		{10.4230/LIPIcs.TYPES.2024.5},
  annote =	{Keywords: Dependent type theory, Bidirectional typing, Observational equality, Normalisation by evaluation}
}
Document
DOI: 10.4230/OASIcs.FMBC.2025.10
Program Logics for Ledgers

Authors: Orestis Melkonian, Wouter Swierstra, and James Chapman

Published in: OASIcs, Volume 129, 6th International Workshop on Formal Methods for Blockchains (FMBC 2025)

Abstract
Distributed ledgers nowadays manage substantial monetary funds in the form of cryptocurrencies such as Bitcoin, Ethereum, and Cardano. For such ledgers to be safe, operations that add new entries must be cryptographically sound - but it is less clear how to reason effectively about such ever-growing linear data structures. This paper demonstrates how distributed ledgers may be viewed as computer programs, that, when executed, transfer funds between various parties. As a result, familiar program logics, such as Hoare logic, are applied in a novel setting. Borrowing ideas from concurrent separation logic, this enables modular reasoning principles over arbitrary fragments of any ledger. All of our results have been mechanised in the Agda proof assistant.
Cite as

Orestis Melkonian, Wouter Swierstra, and James Chapman. Program Logics for Ledgers. In 6th International Workshop on Formal Methods for Blockchains (FMBC 2025). Open Access Series in Informatics (OASIcs), Volume 129, pp. 10:1-10:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{melkonian_et_al:OASIcs.FMBC.2025.10,
  author =	{Melkonian, Orestis and Swierstra, Wouter and Chapman, James},
  title =	{{Program Logics for Ledgers}},
  booktitle =	{6th International Workshop on Formal Methods for Blockchains (FMBC 2025)},
  pages =	{10:1--10:22},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-371-3},
  ISSN =	{2190-6807},
  year =	{2025},
  volume =	{129},
  editor =	{Marmsoler, Diego and Xu, Meng},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FMBC.2025.10},
  URN =		{urn:nbn:de:0030-drops-230370},
  doi =		{10.4230/OASIcs.FMBC.2025.10},
  annote =	{Keywords: blockchain, distributed ledgers, UTxO separation logic, program semantics, formal verification, Agda}
}
Artifact
Software
DOI: 10.4230/artifacts.22493
Directed Topology Lean 4

Authors: Dominique Lawson

Abstract
Cite as

Dominique Lawson. Directed Topology Lean 4 (Software, Lean Code). Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@misc{dagstuhl-artifact-22493,
   title = {{Directed Topology Lean 4}}, 
   author = {Lawson, Dominique},
   note = {Software, version 1.1., swhId: \href{https://archive.softwareheritage.org/swh:1:dir:479a73373a2bf508149f7d1b889b42304fe78a9e;origin=https://github.com/Dominique-Lawson/Directed-Topology-Lean-4;visit=swh:1:snp:a7554a8cd1b293b90366ad72928c60031a03f19c;anchor=swh:1:rev:009529606c66d37ef93b4b81b8587f71ce4d2c56}{\texttt{swh:1:dir:479a73373a2bf508149f7d1b889b42304fe78a9e}} (visited on 2024-11-28)},
   url = {https://github.com/Dominique-Lawson/Directed-Topology-Lean-4},
   doi = {10.4230/artifacts.22493},
}
Document
DOI: 10.4230/LIPIcs.ITP.2024.8
The Directed Van Kampen Theorem in Lean

Authors: Henning Basold, Peter Bruin, and Dominique Lawson

Published in: LIPIcs, Volume 309, 15th International Conference on Interactive Theorem Proving (ITP 2024)

Abstract
Directed topology augments the concept of a topological space with a notion of directed paths. This leads to a category of directed spaces, in which the morphisms are continuous maps respecting directed paths. Directed topology thereby enables an accurate representation of computation paths in concurrent systems that usually cannot be reversed. Even though ideas from algebraic topology have analogues in directed topology, the directedness drastically changes how spaces can be characterised. For instance, while an important homotopy invariant of a topological space is its fundamental groupoid, for directed spaces this has to be replaced by the fundamental category because directed paths are not necessarily reversible. In this paper, we present a Lean 4 formalisation of directed spaces and of a Van Kampen theorem for them, which allows the fundamental category of a directed space to be computed in terms of the fundamental categories of subspaces. Part of this formalisation is also a significant theory of directed spaces, directed homotopy theory and path coverings, which can serve as basis for future formalisations of directed topology. The formalisation in Lean can also be used in computer-assisted reasoning about the behaviour of concurrent systems that have been represented as directed spaces.
Cite as

Henning Basold, Peter Bruin, and Dominique Lawson. The Directed Van Kampen Theorem in Lean. In 15th International Conference on Interactive Theorem Proving (ITP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 309, pp. 8:1-8:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{basold_et_al:LIPIcs.ITP.2024.8,
  author =	{Basold, Henning and Bruin, Peter and Lawson, Dominique},
  title =	{{The Directed Van Kampen Theorem in Lean}},
  booktitle =	{15th International Conference on Interactive Theorem Proving (ITP 2024)},
  pages =	{8:1--8:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-337-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{309},
  editor =	{Bertot, Yves and Kutsia, Temur and Norrish, Michael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2024.8},
  URN =		{urn:nbn:de:0030-drops-207368},
  doi =		{10.4230/LIPIcs.ITP.2024.8},
  annote =	{Keywords: Lean, Directed Topology, Van Kampen Theorem, Directed Homotopy Theory, Formalised Mathematics}
}
Document
DOI: 10.4230/LIPIcs.FSCD.2024.25
Substitution for Non-Wellfounded Syntax with Binders Through Monoidal Categories

Authors: Ralph Matthes, Kobe Wullaert, and Benedikt Ahrens

Published in: LIPIcs, Volume 299, 9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024)

Abstract
We describe a generic construction of non-wellfounded syntax involving variable binding and its monadic substitution operation. Our construction of the syntax and its substitution takes place in category theory, notably by using monoidal categories and strong functors between them. A language is specified by a multi-sorted binding signature, say Σ. First, we provide sufficient criteria for Σ to generate a language of possibly infinite terms, through ω-continuity. Second, we construct a monadic substitution operation for the language generated by Σ. A cornerstone in this construction is a mild generalization of the notion of heterogeneous substitution systems developed by Matthes and Uustalu; such a system encapsulates the necessary corecursion scheme for implementing substitution. The results are formalized in the Coq proof assistant, through the UniMath library of univalent mathematics.
Cite as

Ralph Matthes, Kobe Wullaert, and Benedikt Ahrens. Substitution for Non-Wellfounded Syntax with Binders Through Monoidal Categories. In 9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 299, pp. 25:1-25:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{matthes_et_al:LIPIcs.FSCD.2024.25,
  author =	{Matthes, Ralph and Wullaert, Kobe and Ahrens, Benedikt},
  title =	{{Substitution for Non-Wellfounded Syntax with Binders Through Monoidal Categories}},
  booktitle =	{9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024)},
  pages =	{25:1--25:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-323-2},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{299},
  editor =	{Rehof, Jakob},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSCD.2024.25},
  URN =		{urn:nbn:de:0030-drops-203540},
  doi =		{10.4230/LIPIcs.FSCD.2024.25},
  annote =	{Keywords: Non-wellfounded syntax, Substitution, Monoidal categories, Actegories, Tensorial strength, Proof assistant Coq, UniMath library}
}
Document
DOI: 10.4230/LIPIcs.CALCO.2023.18
Composition and Recursion for Causal Structures

Authors: Henning Basold and Tanjona Ralaivaosaona

Published in: LIPIcs, Volume 270, 10th Conference on Algebra and Coalgebra in Computer Science (CALCO 2023)

Abstract
Causality appears in various contexts as a property where present behaviour can only depend on past events, but not on future events. In this paper, we compare three different notions of causality that capture the idea of causality in the form of restrictions on morphisms between coinductively defined structures, such as final coalgebras and chains, in fairly general categories. We then focus on one presentation and show that it gives rise to a traced symmetric monoidal category of causal morphisms. This shows that causal morphisms are closed under sequential and parallel composition and, crucially, under recursion.
Cite as

Henning Basold and Tanjona Ralaivaosaona. Composition and Recursion for Causal Structures. In 10th Conference on Algebra and Coalgebra in Computer Science (CALCO 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 270, pp. 18:1-18:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{basold_et_al:LIPIcs.CALCO.2023.18,
  author =	{Basold, Henning and Ralaivaosaona, Tanjona},
  title =	{{Composition and Recursion for Causal Structures}},
  booktitle =	{10th Conference on Algebra and Coalgebra in Computer Science (CALCO 2023)},
  pages =	{18:1--18:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-287-7},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{270},
  editor =	{Baldan, Paolo and de Paiva, Valeria},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CALCO.2023.18},
  URN =		{urn:nbn:de:0030-drops-188157},
  doi =		{10.4230/LIPIcs.CALCO.2023.18},
  annote =	{Keywords: Causal morphisms, Final Coalgebras, Final Chains, Metric Maps, Guarded Recursion, Traced Symmetric Monoidal Category}
}
Document
Complete Volume
DOI: 10.4230/LIPIcs.TYPES.2021
LIPIcs, Volume 239, TYPES 2021, Complete Volume

Authors: Henning Basold, Jesper Cockx, and Silvia Ghilezan

Published in: LIPIcs, Volume 239, 27th International Conference on Types for Proofs and Programs (TYPES 2021)

Abstract
LIPIcs, Volume 239, TYPES 2021, Complete Volume
Cite as

27th International Conference on Types for Proofs and Programs (TYPES 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 239, pp. 1-280, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@Proceedings{basold_et_al:LIPIcs.TYPES.2021,
  title =	{{LIPIcs, Volume 239, TYPES 2021, Complete Volume}},
  booktitle =	{27th International Conference on Types for Proofs and Programs (TYPES 2021)},
  pages =	{1--280},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-254-9},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{239},
  editor =	{Basold, Henning and Cockx, Jesper and Ghilezan, Silvia},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TYPES.2021},
  URN =		{urn:nbn:de:0030-drops-167680},
  doi =		{10.4230/LIPIcs.TYPES.2021},
  annote =	{Keywords: LIPIcs, Volume 239, TYPES 2021, Complete Volume}
}
Document
Front Matter
DOI: 10.4230/LIPIcs.TYPES.2021.0
Front Matter, Table of Contents, Preface, Conference Organization

Authors: Henning Basold, Jesper Cockx, and Silvia Ghilezan

Published in: LIPIcs, Volume 239, 27th International Conference on Types for Proofs and Programs (TYPES 2021)

Abstract
Front Matter, Table of Contents, Preface, Conference Organization
Cite as

27th International Conference on Types for Proofs and Programs (TYPES 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 239, pp. 0:i-0:viii, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{basold_et_al:LIPIcs.TYPES.2021.0,
  author =	{Basold, Henning and Cockx, Jesper and Ghilezan, Silvia},
  title =	{{Front Matter, Table of Contents, Preface, Conference Organization}},
  booktitle =	{27th International Conference on Types for Proofs and Programs (TYPES 2021)},
  pages =	{0:i--0:viii},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-254-9},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{239},
  editor =	{Basold, Henning and Cockx, Jesper and Ghilezan, Silvia},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TYPES.2021.0},
  URN =		{urn:nbn:de:0030-drops-167691},
  doi =		{10.4230/LIPIcs.TYPES.2021.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, Conference Organization}
}
Document
DOI: 10.4230/LIPIcs.TYPES.2021.1
Verification of Bitcoin Script in Agda Using Weakest Preconditions for Access Control

Authors: Fahad F. Alhabardi, Arnold Beckmann, Bogdan Lazar, and Anton Setzer

Published in: LIPIcs, Volume 239, 27th International Conference on Types for Proofs and Programs (TYPES 2021)

Abstract
This paper contributes to the verification of programs written in Bitcoin’s smart contract language script in the interactive theorem prover Agda. It focuses on the security property of access control for script programs that govern the distribution of Bitcoins. It advocates that weakest preconditions in the context of Hoare triples are the appropriate notion for verifying access control. It aims at obtaining human-readable descriptions of weakest preconditions in order to close the validation gap between user requirements and formal specification of smart contracts. As examples for the proposed approach, the paper focuses on two standard script programs that govern the distribution of Bitcoins, Pay to Public Key Hash (P2PKH) and Pay to Multisig (P2MS). The paper introduces an operational semantics of the script commands used in P2PKH and P2MS, which is formalised in the Agda proof assistant and reasoned about using Hoare triples. Two methodologies for obtaining human-readable descriptions of weakest preconditions are discussed: (1) a step-by-step approach, which works backwards instruction by instruction through a script, sometimes grouping several instructions together; (2) symbolic execution of the code and translation into a nested case distinction, which allows to read off weakest preconditions as the disjunction of conjunctions of conditions along accepting paths. A syntax for equational reasoning with Hoare Triples is defined in order to formalise those approaches in Agda.
Cite as

Fahad F. Alhabardi, Arnold Beckmann, Bogdan Lazar, and Anton Setzer. Verification of Bitcoin Script in Agda Using Weakest Preconditions for Access Control. In 27th International Conference on Types for Proofs and Programs (TYPES 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 239, pp. 1:1-1:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{alhabardi_et_al:LIPIcs.TYPES.2021.1,
  author =	{Alhabardi, Fahad F. and Beckmann, Arnold and Lazar, Bogdan and Setzer, Anton},
  title =	{{Verification of Bitcoin Script in Agda Using Weakest Preconditions for Access Control}},
  booktitle =	{27th International Conference on Types for Proofs and Programs (TYPES 2021)},
  pages =	{1:1--1:25},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-254-9},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{239},
  editor =	{Basold, Henning and Cockx, Jesper and Ghilezan, Silvia},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TYPES.2021.1},
  URN =		{urn:nbn:de:0030-drops-167704},
  doi =		{10.4230/LIPIcs.TYPES.2021.1},
  annote =	{Keywords: Blockchain, Cryptocurrency, Bitcoin, Agda, Verification, Hoare logic, Bitcoin Script, P2PKH, P2MS, Access control, Weakest precondition, Predicate transformer semantics, Provable correctness, Symbolic execution, Smart contracts}
}
Document
DOI: 10.4230/LIPIcs.TYPES.2021.2
Formalisation of Dependent Type Theory: The Example of CaTT

Authors: Thibaut Benjamin

Published in: LIPIcs, Volume 239, 27th International Conference on Types for Proofs and Programs (TYPES 2021)

Abstract
We present the type theory CaTT, originally introduced by Finster and Mimram to describe globular weak ω-categories, formalise this theory in the language of homotopy type theory and discuss connections with the open problem internalising higher structures. Most of the studies about this type theory assume that it is well-formed and satisfy the usual syntactic properties that dependent type theories enjoy, without being completely clear and thorough about what these properties are exactly. We use our formalisation to list and formally prove all of these meta-properties, thus filling a gap in the foundational aspect. We discuss the aspects of the formalisation inherent to CaTT. We present the formalisation in a way that not only handles the type theory CaTT but also related type theories that share the same structure, and in particular we show that this formalisation provides a proper ground to the study of the theory MCaTT which describes the globular monoidal weak ω-categories. The article is accompanied by a development in the proof assistant Agda to check the formalisation that we present.
Cite as

Thibaut Benjamin. Formalisation of Dependent Type Theory: The Example of CaTT. In 27th International Conference on Types for Proofs and Programs (TYPES 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 239, pp. 2:1-2:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{benjamin:LIPIcs.TYPES.2021.2,
  author =	{Benjamin, Thibaut},
  title =	{{Formalisation of Dependent Type Theory: The Example of CaTT}},
  booktitle =	{27th International Conference on Types for Proofs and Programs (TYPES 2021)},
  pages =	{2:1--2:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-254-9},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{239},
  editor =	{Basold, Henning and Cockx, Jesper and Ghilezan, Silvia},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TYPES.2021.2},
  URN =		{urn:nbn:de:0030-drops-167719},
  doi =		{10.4230/LIPIcs.TYPES.2021.2},
  annote =	{Keywords: Dependent type theory, homotopy type theory, higher categories, formalisation, Agda, proof assistant}
}
Document
DOI: 10.4230/LIPIcs.TYPES.2021.3
Strictification of Weakly Stable Type-Theoretic Structures Using Generic Contexts

Authors: Rafaël Bocquet

Published in: LIPIcs, Volume 239, 27th International Conference on Types for Proofs and Programs (TYPES 2021)

Abstract
We present a new strictification method for type-theoretic structures that are only weakly stable under substitution. Given weakly stable structures over some model of type theory, we construct equivalent strictly stable structures by evaluating the weakly stable structures at generic contexts. These generic contexts are specified using the categorical notion of familial representability. This generalizes the local universes method of Lumsdaine and Warren. We show that generic contexts can also be constructed in any category with families which is freely generated by collections of types and terms, without any definitional equality. This relies on the fact that they support first-order unification. These free models can only be equipped with weak type-theoretic structures, whose computation rules are given by typal equalities. Our main result is that any model of type theory with weakly stable weak type-theoretic structures admits an equivalent model with strictly stable weak type-theoretic structures.
Cite as

Rafaël Bocquet. Strictification of Weakly Stable Type-Theoretic Structures Using Generic Contexts. In 27th International Conference on Types for Proofs and Programs (TYPES 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 239, pp. 3:1-3:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{bocquet:LIPIcs.TYPES.2021.3,
  author =	{Bocquet, Rafa\"{e}l},
  title =	{{Strictification of Weakly Stable Type-Theoretic Structures Using Generic Contexts}},
  booktitle =	{27th International Conference on Types for Proofs and Programs (TYPES 2021)},
  pages =	{3:1--3:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-254-9},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{239},
  editor =	{Basold, Henning and Cockx, Jesper and Ghilezan, Silvia},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TYPES.2021.3},
  URN =		{urn:nbn:de:0030-drops-167724},
  doi =		{10.4230/LIPIcs.TYPES.2021.3},
  annote =	{Keywords: type theory, strictification, coherence, familial representability, unification}
}
Document
DOI: 10.4230/LIPIcs.TYPES.2021.4
A Machine-Checked Proof of Birkhoff’s Variety Theorem in Martin-Löf Type Theory

Authors: William DeMeo and Jacques Carette

Published in: LIPIcs, Volume 239, 27th International Conference on Types for Proofs and Programs (TYPES 2021)

Abstract
The Agda Universal Algebra Library is a project aimed at formalizing the foundations of universal algebra, equational logic and model theory in dependent type theory using Agda. In this paper we draw from many components of the library to present a self-contained, formal, constructive proof of Birkhoff’s HSP theorem in Martin-Löf dependent type theory. This achieves one of the project’s initial goals: to demonstrate the expressive power of inductive and dependent types for representing and reasoning about general algebraic and relational structures by using them to formalize a significant theorem in the field.
Cite as

William DeMeo and Jacques Carette. A Machine-Checked Proof of Birkhoff’s Variety Theorem in Martin-Löf Type Theory. In 27th International Conference on Types for Proofs and Programs (TYPES 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 239, pp. 4:1-4:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{demeo_et_al:LIPIcs.TYPES.2021.4,
  author =	{DeMeo, William and Carette, Jacques},
  title =	{{A Machine-Checked Proof of Birkhoff’s Variety Theorem in Martin-L\"{o}f Type Theory}},
  booktitle =	{27th International Conference on Types for Proofs and Programs (TYPES 2021)},
  pages =	{4:1--4:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-254-9},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{239},
  editor =	{Basold, Henning and Cockx, Jesper and Ghilezan, Silvia},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TYPES.2021.4},
  URN =		{urn:nbn:de:0030-drops-167737},
  doi =		{10.4230/LIPIcs.TYPES.2021.4},
  annote =	{Keywords: Agda, constructive mathematics, dependent types, equational logic, formal verification, Martin-L\"{o}f type theory, model theory, universal algebra}
}
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