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Documents authored by Gonzalez Boix, Elisa


Document
Ensuring Convergence and Invariants Without Coordination

Authors: Dina Borrego, Nuno Preguiça, Elisa Gonzalez Boix, and Carla Ferreira

Published in: LIPIcs, Volume 333, 39th European Conference on Object-Oriented Programming (ECOOP 2025)


Abstract
The CAP theorem demonstrates a trade-off between consistency and availability (and, by extension, latency) in systems where network partitions are unavoidable, such as in cloud computing and local-first software. While adopting weak consistency can preserve availability, it may result in inconsistencies that compromise application correctness. Replicated data types provide a principled, coordination-free approach to guarantee convergence but do not consider application invariants. Existing methods for maintaining invariants in replicated systems either rely on coordination - undermining the benefits of weak consistency - or suffer from limited applicability. This paper introduces the No-Op framework, a generic approach for enforcing consistency without coordination while guaranteeing both convergence and invariant preservation. The core idea of the No-Op approach is to resolve conflicts among concurrent operations by prioritising one operation over the other according to programmer-defined conflict resolution policies. This prioritisation transforms the less-preferred operation into a no-side-effect operation, ensuring conflict-free execution. We formalise the model underlying the No-Op framework and introduce a replication protocol built upon it, accompanied by a formal proof of correctness for both the framework and the protocol. Furthermore, we demonstrate the framework’s applicability by showcasing the design of widely used replicated data types and the preservation of a wide range of application invariants.

Cite as

Dina Borrego, Nuno Preguiça, Elisa Gonzalez Boix, and Carla Ferreira. Ensuring Convergence and Invariants Without Coordination. In 39th European Conference on Object-Oriented Programming (ECOOP 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 333, pp. 4:1-4:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)


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@InProceedings{borrego_et_al:LIPIcs.ECOOP.2025.4,
  author =	{Borrego, Dina and Pregui\c{c}a, Nuno and Gonzalez Boix, Elisa and Ferreira, Carla},
  title =	{{Ensuring Convergence and Invariants Without Coordination}},
  booktitle =	{39th European Conference on Object-Oriented Programming (ECOOP 2025)},
  pages =	{4:1--4:29},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-373-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{333},
  editor =	{Aldrich, Jonathan and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2025.4},
  URN =		{urn:nbn:de:0030-drops-232978},
  doi =		{10.4230/LIPIcs.ECOOP.2025.4},
  annote =	{Keywords: distributed systems, conflict resolution, RDTs, invariant preservation}
}
Document
Wastrumentation: Portable WebAssembly Dynamic Analysis with Support for Intercession

Authors: Aäron Munsters, Angel Luis Scull Pupo, and Elisa Gonzalez Boix

Published in: LIPIcs, Volume 333, 39th European Conference on Object-Oriented Programming (ECOOP 2025)


Abstract
Dynamic program analyses help in understanding a program’s runtime behavior and detect issues related to security, program comprehension, or profiling. Instrumentation platforms aid analysis developers by offering a high-level API to write the analysis, and inserting the analysis into the target program. However, current instrumentation platforms for WebAssembly (Wasm) restrict analysis portability because they require concrete runtime environments. Moreover, their analysis API only allows the development of analyses that observe the target program but cannot modify it. As a result, many popular dynamic analyses present for other languages, such as runtime hardening, virtual patching or runtime optimization, cannot currently be implemented for Wasm atop a dynamic analysis platform. Instead, they need to be built manually, which requires knowledge of low-level details of the Wasm’s semantics and instruction set, and how to safely manipulate it. This paper introduces Wastrumentation, the first dynamic analysis platform for WebAssembly that supports intercession. Our solution, based on source code instrumentation, weaves the analysis code directly into the target program code. Inlining the analysis into the target’s source code avoids dependencies on the runtime environment, making analyses portable across Wasm VMs. Moreover, it enables the implementation of analyses in any Wasm-compatible language. We evaluate our solution in two ways. First, we compare it against a state-of-the-art source code instrumentation platform using the WasmR3 benchmarks. The results show improved memory consumption and competitive performance overhead. Second, we develop an extensive portfolio of dynamic analyses, including novel analyses previously unattainable with source code instrumentation platforms, such as memoization, safe heap access, and the removal of NaN non-determinism.

Cite as

Aäron Munsters, Angel Luis Scull Pupo, and Elisa Gonzalez Boix. Wastrumentation: Portable WebAssembly Dynamic Analysis with Support for Intercession. In 39th European Conference on Object-Oriented Programming (ECOOP 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 333, pp. 23:1-23:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)


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@InProceedings{munsters_et_al:LIPIcs.ECOOP.2025.23,
  author =	{Munsters, A\"{a}ron and Scull Pupo, Angel Luis and Gonzalez Boix, Elisa},
  title =	{{Wastrumentation: Portable WebAssembly Dynamic Analysis with Support for Intercession}},
  booktitle =	{39th European Conference on Object-Oriented Programming (ECOOP 2025)},
  pages =	{23:1--23:29},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-373-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{333},
  editor =	{Aldrich, Jonathan and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2025.23},
  URN =		{urn:nbn:de:0030-drops-233153},
  doi =		{10.4230/LIPIcs.ECOOP.2025.23},
  annote =	{Keywords: WebAssembly, dynamic analysis, instrumentation platform, intercession}
}
Document
Artifact
Ensuring Convergence and Invariants Without Coordination (Artifact)

Authors: Dina Borrego, Nuno Preguiça, Elisa Gonzalez Boix, and Carla Ferreira

Published in: DARTS, Volume 11, Issue 2, Special Issue of the 39th European Conference on Object-Oriented Programming (ECOOP 2025)


Abstract
Our related paper introduces the No-Op framework, a generic approach for enforcing consistency without coordination while guaranteeing both convergence and invariant preservation. We implemented the core of the No-Op replication protocol in VeriFx [De Porre et al., 2023], a programming language for RDTs with automated proof capabilities. Alongside the algorithm implementation, we developed formal proofs to automatically verify the algorithm’s correctness properties when applied to specific data types or application implementations. This artifact bundles the implementation of the No-Op framework, various CRDTs [Marc Shapiro et al., 2011], and an eBay-like auction system akin to the RUBiS system [Emmanuel Cecchet et al., 2002] described in Section 5 of the paper. The artifact also provides a Dockerfile that can be used to reproduce the verification results (Section 4 of the paper).

Cite as

Dina Borrego, Nuno Preguiça, Elisa Gonzalez Boix, and Carla Ferreira. Ensuring Convergence and Invariants Without Coordination (Artifact). In Special Issue of the 39th European Conference on Object-Oriented Programming (ECOOP 2025). Dagstuhl Artifacts Series (DARTS), Volume 11, Issue 2, pp. 1:1-1:7, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)


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@Article{borrego_et_al:DARTS.11.2.1,
  author =	{Borrego, Dina and Pregui\c{c}a, Nuno and Gonzalez Boix, Elisa and Ferreira, Carla},
  title =	{{Ensuring Convergence and Invariants Without Coordination (Artifact)}},
  pages =	{1:1--1:7},
  journal =	{Dagstuhl Artifacts Series},
  ISSN =	{2509-8195},
  year =	{2025},
  volume =	{11},
  number =	{2},
  editor =	{Borrego, Dina and Pregui\c{c}a, Nuno and Gonzalez Boix, Elisa and Ferreira, Carla},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DARTS.11.2.1},
  URN =		{urn:nbn:de:0030-drops-233447},
  doi =		{10.4230/DARTS.11.2.1},
  annote =	{Keywords: distributed systems, conflict resolution, RDTs, invariant preservation}
}
Document
Nested Pure Operation-Based CRDTs

Authors: Jim Bauwens and Elisa Gonzalez Boix

Published in: LIPIcs, Volume 263, 37th European Conference on Object-Oriented Programming (ECOOP 2023)


Abstract
Modern distributed applications increasingly replicate data to guarantee high availability and optimal user experience. Conflict-free Replicated Data Types (CRDTs) are a family of data types specially designed for highly available systems that guarantee some form of eventual consistency. Designing CRDTs is very difficult because it requires devising designs that guarantee convergence in the presence of conflicting operations. Even though design patterns and structured frameworks have emerged to aid developers with this problem, they mostly focus on statically structured data; nesting and dynamically changing the structure of a CRDT remains to be an open issue. This paper explores support for nested CRDTs in a structured and systematic way. To this end, we define an approach for building nested CRDTs based on the work of pure operation-based CRDTs, resulting in nested pure operation-based CRDTs. We add constructs to control the nesting of CRDTs into a pure operation-based CRDT framework and show how several well-known CRDT designs can be defined in our framework. We provide an implementation of nested pure operation-based CRDTs as an extension to the Flec, an existing TypeScript-based framework for pure operation-based CRDTs. We validate our approach, 1) by implementing a portfolio of nested data structures, 2) by implementing and verifying our approach in the VeriFx language, and 3) by implementing a real-world application scenario and comparing its network usage against an implementation in the closest related work, Automerge. We show that the framework is general enough to nest well-known CRDT designs like maps and lists, and its performance in terms of network traffic is comparable to the state of the art.

Cite as

Jim Bauwens and Elisa Gonzalez Boix. Nested Pure Operation-Based CRDTs. In 37th European Conference on Object-Oriented Programming (ECOOP 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 263, pp. 2:1-2:26, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


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@InProceedings{bauwens_et_al:LIPIcs.ECOOP.2023.2,
  author =	{Bauwens, Jim and Gonzalez Boix, Elisa},
  title =	{{Nested Pure Operation-Based CRDTs}},
  booktitle =	{37th European Conference on Object-Oriented Programming (ECOOP 2023)},
  pages =	{2:1--2:26},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-281-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{263},
  editor =	{Ali, Karim and Salvaneschi, Guido},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2023.2},
  URN =		{urn:nbn:de:0030-drops-181950},
  doi =		{10.4230/LIPIcs.ECOOP.2023.2},
  annote =	{Keywords: CRDTs, replication, pure operation-based CRDTs, composition, nesting}
}
Document
VeriFx: Correct Replicated Data Types for the Masses

Authors: Kevin De Porre, Carla Ferreira, and Elisa Gonzalez Boix

Published in: LIPIcs, Volume 263, 37th European Conference on Object-Oriented Programming (ECOOP 2023)


Abstract
Distributed systems adopt weak consistency to ensure high availability and low latency, but state convergence is hard to guarantee due to conflicts. Experts carefully design replicated data types (RDTs) that resemble sequential data types and embed conflict resolution mechanisms that ensure convergence. Designing RDTs is challenging as their correctness depends on subtleties such as the ordering of concurrent operations. Currently, researchers manually verify RDTs, either by paper proofs or using proof assistants. Unfortunately, paper proofs are subject to reasoning flaws and mechanized proofs verify a formalization instead of a real-world implementation. Furthermore, writing mechanized proofs is reserved for verification experts and is extremely time-consuming. To simplify the design, implementation, and verification of RDTs, we propose VeriFx, a specialized programming language for RDTs with automated proof capabilities. VeriFx lets programmers implement RDTs atop functional collections and express correctness properties that are verified automatically. Verified RDTs can be transpiled to mainstream languages (currently Scala and JavaScript). VeriFx provides libraries for implementing and verifying Conflict-free Replicated Data Types (CRDTs) and Operational Transformation (OT) functions. These libraries implement the general execution model of those approaches and define their correctness properties. We use the libraries to implement and verify an extensive portfolio of 51 CRDTs, 16 of which are used in industrial databases, and reproduce a study on the correctness of OT functions.

Cite as

Kevin De Porre, Carla Ferreira, and Elisa Gonzalez Boix. VeriFx: Correct Replicated Data Types for the Masses. In 37th European Conference on Object-Oriented Programming (ECOOP 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 263, pp. 9:1-9:45, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


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@InProceedings{deporre_et_al:LIPIcs.ECOOP.2023.9,
  author =	{De Porre, Kevin and Ferreira, Carla and Gonzalez Boix, Elisa},
  title =	{{VeriFx: Correct Replicated Data Types for the Masses}},
  booktitle =	{37th European Conference on Object-Oriented Programming (ECOOP 2023)},
  pages =	{9:1--9:45},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-281-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{263},
  editor =	{Ali, Karim and Salvaneschi, Guido},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2023.9},
  URN =		{urn:nbn:de:0030-drops-182028},
  doi =		{10.4230/LIPIcs.ECOOP.2023.9},
  annote =	{Keywords: distributed systems, eventual consistency, replicated data types, verification}
}
Document
Artifact
VeriFx: Correct Replicated Data Types for the Masses (Artifact)

Authors: Kevin De Porre, Carla Ferreira, and Elisa Gonzalez Boix

Published in: DARTS, Volume 9, Issue 2, Special Issue of the 37th European Conference on Object-Oriented Programming (ECOOP 2023)


Abstract
Our related article presents our novel verification language, called VeriFx. We used VeriFx to implement and verify 51 Conflict-Free Replicated Data Types (CRDTs) and 9 Operational Transformation (OT) functions. This artifact bundles the implementation of the various CRDTs and OT functions described in the article. The artifact also contains a Docker file that can be used to reproduce the verification results (Table 1 and 2 in the article). In addition, the artifact can also be used to run custom VeriFx programs and verify their correctness.

Cite as

Kevin De Porre, Carla Ferreira, and Elisa Gonzalez Boix. VeriFx: Correct Replicated Data Types for the Masses (Artifact). In Special Issue of the 37th European Conference on Object-Oriented Programming (ECOOP 2023). Dagstuhl Artifacts Series (DARTS), Volume 9, Issue 2, pp. 19:1-19:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


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@Article{deporre_et_al:DARTS.9.2.19,
  author =	{De Porre, Kevin and Ferreira, Carla and Gonzalez Boix, Elisa},
  title =	{{VeriFx: Correct Replicated Data Types for the Masses (Artifact)}},
  pages =	{19:1--19:2},
  journal =	{Dagstuhl Artifacts Series},
  ISSN =	{2509-8195},
  year =	{2023},
  volume =	{9},
  number =	{2},
  editor =	{De Porre, Kevin and Ferreira, Carla and Gonzalez Boix, Elisa},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DARTS.9.2.19},
  URN =		{urn:nbn:de:0030-drops-182596},
  doi =		{10.4230/DARTS.9.2.19},
  annote =	{Keywords: distributed systems, eventual consistency, replicated data types, verification}
}
Document
Brave New Idea Paper
Multiverse Debugging: Non-Deterministic Debugging for Non-Deterministic Programs (Brave New Idea Paper)

Authors: Carmen Torres Lopez, Robbert Gurdeep Singh, Stefan Marr, Elisa Gonzalez Boix, and Christophe Scholliers

Published in: LIPIcs, Volume 134, 33rd European Conference on Object-Oriented Programming (ECOOP 2019)


Abstract
Many of today’s software systems are parallel or concurrent. With the rise of Node.js and more generally event-loop architectures, many systems need to handle concurrency. However, its non-deterministic behavior makes it hard to reproduce bugs. Today’s interactive debuggers unfortunately do not support developers in debugging non-deterministic issues. They only allow us to explore a single execution path. Therefore, some bugs may never be reproduced in the debugging session, because the right conditions are not triggered. As a solution, we propose multiverse debugging, a new approach for debugging non-deterministic programs that allows developers to observe all possible execution paths of a parallel program and debug it interactively. We introduce the concepts of multiverse breakpoints and stepping, which can halt a program in different execution paths, i.e. universes. We apply multiverse debugging to AmbientTalk, an actor-based language, resulting in Voyager, a multiverse debugger implemented on top of the AmbientTalk operational semantics. We provide a proof of non-interference, i.e., we prove that observing the behavior of a program by the debugger does not affect the behavior of that program and vice versa. Multiverse debugging establishes the foundation for debugging non-deterministic programs interactively, which we believe can aid the development of parallel and concurrent systems.

Cite as

Carmen Torres Lopez, Robbert Gurdeep Singh, Stefan Marr, Elisa Gonzalez Boix, and Christophe Scholliers. Multiverse Debugging: Non-Deterministic Debugging for Non-Deterministic Programs (Brave New Idea Paper). In 33rd European Conference on Object-Oriented Programming (ECOOP 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 134, pp. 27:1-27:30, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)


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@InProceedings{torreslopez_et_al:LIPIcs.ECOOP.2019.27,
  author =	{Torres Lopez, Carmen and Gurdeep Singh, Robbert and Marr, Stefan and Gonzalez Boix, Elisa and Scholliers, Christophe},
  title =	{{Multiverse Debugging: Non-Deterministic Debugging for Non-Deterministic Programs}},
  booktitle =	{33rd European Conference on Object-Oriented Programming (ECOOP 2019)},
  pages =	{27:1--27:30},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-111-5},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{134},
  editor =	{Donaldson, Alastair F.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2019.27},
  URN =		{urn:nbn:de:0030-drops-108192},
  doi =		{10.4230/LIPIcs.ECOOP.2019.27},
  annote =	{Keywords: Debugging, Parallelism, Concurrency, Actors, Formal Semantics}
}
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