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Documents authored by Chapman, James

Document
DOI: 10.4230/OASIcs.FMBC.2025.7
A Readable and Computable Formalization of the Streamlet Consensus Protocol

Authors: Mauro Jaskelioff, Orestis Melkonian, and James Chapman

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

Abstract
Consensus protocols are the fundamental building block of blockchain technology. Hence, correctness of the consensus protocol is essential for the construction of a reliable system. In the past few years, we saw the introduction of a myriad of new protocols of the BFT family of consensus protocols. The Streamlet protocol is one of these new protocols, which while not the fastest, it is certainly the simplest one. In order to have strong guarantees for the protocol and its implementations we want to obtain formalizations that are readable enough to be used to communicate between formalizers and implementors, that have a mechanized proof of correctness and that can support the testing of implementations. We present a readable and computable formalization of the Streamlet protocol in Agda, provide a mechanization of its proof of consistency, and show how one may use the formalization for testing implementations of it.
Cite as

Mauro Jaskelioff, Orestis Melkonian, and James Chapman. A Readable and Computable Formalization of the Streamlet Consensus Protocol. In 6th International Workshop on Formal Methods for Blockchains (FMBC 2025). Open Access Series in Informatics (OASIcs), Volume 129, pp. 7:1-7:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{jaskelioff_et_al:OASIcs.FMBC.2025.7,
  author =	{Jaskelioff, Mauro and Melkonian, Orestis and Chapman, James},
  title =	{{A Readable and Computable Formalization of the Streamlet Consensus Protocol}},
  booktitle =	{6th International Workshop on Formal Methods for Blockchains (FMBC 2025)},
  pages =	{7:1--7:18},
  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.2025.7},
  URN =		{urn:nbn:de:0030-drops-230356},
  doi =		{10.4230/OASIcs.FMBC.2025.7},
  annote =	{Keywords: blockchain, Streamlet, consensus, formal verification, Agda}
}
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.22485
IntersectMBO/formal-ledger-specifications

Authors: Andre Knispel, Orestis Melkonian, James Chapman, Alasdair Hill, Joosep Jääger, William DeMeo, and Ulf Norell

Abstract
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Andre Knispel, Orestis Melkonian, James Chapman, Alasdair Hill, Joosep Jääger, William DeMeo, Ulf Norell. IntersectMBO/formal-ledger-specifications (Software, Agda Code). Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@misc{dagstuhl-artifact-22485,
   title = {{IntersectMBO/formal-ledger-specifications}}, 
   author = {Knispel, Andre and Melkonian, Orestis and Chapman, James and Hill, Alasdair and J\"{a}\"{a}ger, Joosep and DeMeo, William and Norell, Ulf},
   note = {Software, swhId: \href{https://archive.softwareheritage.org/swh:1:dir:085aefb014706c3ee4bcf1a9f85fcceaf10ba4cc;origin=https://github.com/IntersectMBO/formal-ledger-specifications;visit=swh:1:snp:5097bdc07a9030f7e251cb6529989d442bb82f35;anchor=swh:1:rev:002b7226a3af8e5e1068fd0c8fd1fcbb51bba64e}{\texttt{swh:1:dir:085aefb014706c3ee4bcf1a9f85fcceaf10ba4cc}} (visited on 2024-11-28)},
   url = {https://github.com/IntersectMBO/formal-ledger-specifications},
   doi = {10.4230/artifacts.22485},
}
Document
DOI: 10.4230/OASIcs.FMBC.2024.2
Formal Specification of the Cardano Blockchain Ledger, Mechanized in Agda

Authors: Andre Knispel, Orestis Melkonian, James Chapman, Alasdair Hill, Joosep Jääger, William DeMeo, and Ulf Norell

Published in: OASIcs, Volume 118, 5th International Workshop on Formal Methods for Blockchains (FMBC 2024)

Abstract
Blockchain systems comprise critical software that handle substantial monetary funds, rendering them excellent candidates for formal verification. One of their core components is the underlying ledger that does all the accounting: keeping track of transactions and their validity, etc. Unfortunately, previous theoretical studies are typically confined to an idealized setting, while specifications for real implementations are scarce; either the functionality is directly implemented without a proper specification, or at best an informal specification is written on paper. The present work expands beyond prior meta-theoretical investigations of the EUTxO model to encompass the full scale of the Cardano blockchain: our formal specification describes a hierarchy of modular transitions that covers all the intricacies of a realistic blockchain, such as fully expressive smart contracts and decentralized governance. It is mechanized in a proof assistant, thus enjoys a higher standard of rigor: type-checking prevents minor oversights that were frequent in previous informal approaches; key meta-theoretical properties can now be formally proven; it is an executable specification against which the implementation in production is being tested for conformance; and it provides firm foundations for smart contract verification. Apart from a safety net to keep us in check, the formalization also provides a guideline for the ledger design: one informs the other in a symbiotic way, especially in the case of state-of-the-art features like decentralized governance, which is an emerging sub-field of blockchain research that however mandates a more exploratory approach. All the results presented in this paper have been mechanized in the Agda proof assistant and are publicly available. In fact, this document is itself a literate Agda script and all rendered code has been successfully type-checked.
Cite as

Andre Knispel, Orestis Melkonian, James Chapman, Alasdair Hill, Joosep Jääger, William DeMeo, and Ulf Norell. Formal Specification of the Cardano Blockchain Ledger, Mechanized in Agda. In 5th International Workshop on Formal Methods for Blockchains (FMBC 2024). Open Access Series in Informatics (OASIcs), Volume 118, pp. 2:1-2:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{knispel_et_al:OASIcs.FMBC.2024.2,
  author =	{Knispel, Andre and Melkonian, Orestis and Chapman, James and Hill, Alasdair and J\"{a}\"{a}ger, Joosep and DeMeo, William and Norell, Ulf},
  title =	{{Formal Specification of the Cardano Blockchain Ledger, Mechanized in Agda}},
  booktitle =	{5th International Workshop on Formal Methods for Blockchains (FMBC 2024)},
  pages =	{2:1--2:18},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-317-1},
  ISSN =	{2190-6807},
  year =	{2024},
  volume =	{118},
  editor =	{Bernardo, Bruno and Marmsoler, Diego},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FMBC.2024.2},
  URN =		{urn:nbn:de:0030-drops-198673},
  doi =		{10.4230/OASIcs.FMBC.2024.2},
  annote =	{Keywords: blockchain, distributed ledgers, UTxO, Cardano, formal verification, Agda}
}
Document
DOI: 10.4230/OASIcs.FMBC.2024.10
Structured Contracts in the EUTxO Ledger Model

Authors: Polina Vinogradova, Orestis Melkonian, Philip Wadler, Manuel Chakravarty, Jacco Krijnen, Michael Peyton Jones, James Chapman, and Tudor Ferariu

Published in: OASIcs, Volume 118, 5th International Workshop on Formal Methods for Blockchains (FMBC 2024)

Abstract
Blockchain ledgers based on the extended UTxO model support fully expressive smart contracts to specify permissions for performing certain actions, such as spending transaction outputs or minting assets. There have been some attempts to standardize the implementation of stateful programs using this infrastructure, with varying degrees of success. To remedy this, we introduce the framework of structured contracts to formalize what it means for a stateful program to be correctly implemented on the ledger. Using small-step semantics, our approach relates low-level ledger transitions to high-level transitions of the smart contract being specified, thus allowing users to prove that their abstract specification is adequately realized on the blockchain. We argue that the framework is versatile enough to cover a range of examples, in particular proving the equivalence of multiple concrete implementations of the same abstract specification. Building upon prior meta-theoretical results, our results have been mechanized in the Agda proof assistant, paving the way to rigorous verification of smart contracts.
Cite as

Polina Vinogradova, Orestis Melkonian, Philip Wadler, Manuel Chakravarty, Jacco Krijnen, Michael Peyton Jones, James Chapman, and Tudor Ferariu. Structured Contracts in the EUTxO Ledger Model. In 5th International Workshop on Formal Methods for Blockchains (FMBC 2024). Open Access Series in Informatics (OASIcs), Volume 118, pp. 10:1-10:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{vinogradova_et_al:OASIcs.FMBC.2024.10,
  author =	{Vinogradova, Polina and Melkonian, Orestis and Wadler, Philip and Chakravarty, Manuel and Krijnen, Jacco and Jones, Michael Peyton and Chapman, James and Ferariu, Tudor},
  title =	{{Structured Contracts in the EUTxO Ledger Model}},
  booktitle =	{5th International Workshop on Formal Methods for Blockchains (FMBC 2024)},
  pages =	{10:1--10:19},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-317-1},
  ISSN =	{2190-6807},
  year =	{2024},
  volume =	{118},
  editor =	{Bernardo, Bruno and Marmsoler, Diego},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FMBC.2024.10},
  URN =		{urn:nbn:de:0030-drops-198757},
  doi =		{10.4230/OASIcs.FMBC.2024.10},
  annote =	{Keywords: blockchain, ledger, smart contract, formal verification, specification, transition systems, Agda, UTxO, EUTxO, small-step semantics}
}
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