19 Search Results for "Gardner, Philippa"

Document
DOI: 10.4230/LIPIcs.CSL.2026.47
Useful Call-by-Value: A Semantic Interpretation via Quantitative Types

Authors: Pablo Barenbaum, Delia Kesner, and Mariana Milicich

Published in: LIPIcs, Volume 363, 34th EACSL Annual Conference on Computer Science Logic (CSL 2026)

Abstract
Useful evaluation is an optimised evaluation mechanism for functional programming languages. It relies on representing terms with sharing and imposing a restricted notion of useful substitutions, that intuitively disallows copying subterms that do not contribute to the progress of the computation. In particular, useful call-by-value evaluation optimises the standard call-by-value strategy by preserving its original semantics. This preservation result has been shown by means of syntactical rewriting techniques, difficult to adapt to alternative variants of the calculi at play. In this work, we present the first semantic model of useful call-by-value evaluation through the non-idempotent intersection type system 𝒰. Our first contribution is a characterisation of termination for useful call-by-value evaluation via system 𝒰. That is, a term is typable in system 𝒰 if and only if it terminates in the useful call-by-value strategy. As a second contribution, we show that system 𝒰 provides a quantitative interpretation for useful call-by-value evaluation, offering exact step-count information for program evaluation. Our third contribution is that termination in call-by-value and useful call-by-value are equivalent. This ensures in particular that call-by-value, which is (potentially) erasing, and useful call-by-value, which is non-erasing, are observationally equivalent. Even though the specification of the operational semantics of useful evaluation is highly complex, system 𝒰 is notably simple. As far as we know, system 𝒰 is one of the scarce quantitative type systems capturing exactly the substitution step-count for variables and abstractions in an open call-by-value strategy.
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Pablo Barenbaum, Delia Kesner, and Mariana Milicich. Useful Call-by-Value: A Semantic Interpretation via Quantitative Types. In 34th EACSL Annual Conference on Computer Science Logic (CSL 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 363, pp. 47:1-47:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{barenbaum_et_al:LIPIcs.CSL.2026.47,
  author =	{Barenbaum, Pablo and Kesner, Delia and Milicich, Mariana},
  title =	{{Useful Call-by-Value: A Semantic Interpretation via Quantitative Types}},
  booktitle =	{34th EACSL Annual Conference on Computer Science Logic (CSL 2026)},
  pages =	{47:1--47:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-411-6},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{363},
  editor =	{Guerrini, Stefano and K\"{o}nig, Barbara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2026.47},
  URN =		{urn:nbn:de:0030-drops-254721},
  doi =		{10.4230/LIPIcs.CSL.2026.47},
  annote =	{Keywords: Lambda calculus, Evaluation strategies, Call-by-Value, Useful Evaluation, Intersection types, Quantitative models}
}
Document
DOI: 10.4230/LIPIcs.FSTTCS.2025.18
Iterating Non-Aggregative Structure Compositions

Authors: Marius Bozga, Radu Iosif, and Florian Zuleger

Published in: LIPIcs, Volume 360, 45th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2025)

Abstract
An aggregative composition is a binary operation obeying the principle that the whole is determined by the sum of its parts. The development of graph algebras, on which the theory of formal graph languages is built, relies on aggregative compositions that behave like disjoint union, except for a set of well-marked interface vertices from both sides, that are joined. The same style of composition has been considered in the context of relational structures, that generalize graphs and use constant symbols to label the interface. In this paper, we study a non-aggregative composition operation, called fusion, that joins non-deterministically chosen elements from disjoint structures. The sets of structures obtained by iteratively applying fusion do not always have bounded tree-width, even when starting from a tree-width bounded set. First, we prove that the problem of the existence of a bound on the tree-width of the closure of a given set under fusion is decidable, when the input set is described inductively by a finite hyperedge-replacement (HR) grammar, written using the operations of aggregative composition, forgetting and renaming of constants. Such sets are usually called context-free. Second, assuming that the closure under fusion of a context-free set has bounded tree-width, we show that it is the language of an effectively constructible HR grammar. A possible application of the latter result is the possiblity of checking whether all structures from a non-aggregatively closed set having bounded tree-width satisfy a given monadic second order logic formula.
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Marius Bozga, Radu Iosif, and Florian Zuleger. Iterating Non-Aggregative Structure Compositions. In 45th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 360, pp. 18:1-18:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{bozga_et_al:LIPIcs.FSTTCS.2025.18,
  author =	{Bozga, Marius and Iosif, Radu and Zuleger, Florian},
  title =	{{Iterating Non-Aggregative Structure Compositions}},
  booktitle =	{45th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2025)},
  pages =	{18:1--18:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-406-2},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{360},
  editor =	{Aiswarya, C. and Mehta, Ruta and Roy, Subhajit},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2025.18},
  URN =		{urn:nbn:de:0030-drops-250997},
  doi =		{10.4230/LIPIcs.FSTTCS.2025.18},
  annote =	{Keywords: Hyperedge replacement, Tree-width}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.FSCD.2025.3
Unsolvable Terms in Filter Models (Invited Talk)

Authors: Mariangiola Dezani-Ciancaglini, Paola Giannini, and Furio Honsell

Published in: LIPIcs, Volume 337, 10th International Conference on Formal Structures for Computation and Deduction (FSCD 2025)

Abstract
Intersection type theories (itt’s) and filter models, i.e. λ-calculus models generated by itt’s, are reviewed in full generality. In this framework, which subsumes most λ-calculus models in the literature based on Scott-continuous functions, we discuss the interpretation of unsolvable terms. We give a necessary, but not sufficient, condition on an itt for the interpretation of some unsolvable term to be non-trivial in the filter model it generates. This result is obtained building on a type theoretic characterisation of the fine structure of unsolvables.
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Mariangiola Dezani-Ciancaglini, Paola Giannini, and Furio Honsell. Unsolvable Terms in Filter Models (Invited Talk). In 10th International Conference on Formal Structures for Computation and Deduction (FSCD 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 337, pp. 3:1-3:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{dezaniciancaglini_et_al:LIPIcs.FSCD.2025.3,
  author =	{Dezani-Ciancaglini, Mariangiola and Giannini, Paola and Honsell, Furio},
  title =	{{Unsolvable Terms in Filter Models}},
  booktitle =	{10th International Conference on Formal Structures for Computation and Deduction (FSCD 2025)},
  pages =	{3:1--3:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-374-4},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{337},
  editor =	{Fern\'{a}ndez, Maribel},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSCD.2025.3},
  URN =		{urn:nbn:de:0030-drops-236181},
  doi =		{10.4230/LIPIcs.FSCD.2025.3},
  annote =	{Keywords: \lambda-calculus, Intersection Types, Unsolvable Terms, Filter Models}
}
Document
DOI: 10.4230/LIPIcs.FSCD.2025.7
Combining Generalization Algorithms in Regular Collapse-Free Theories

Authors: Mauricio Ayala-Rincón, David M. Cerna, Temur Kutsia, and Christophe Ringeissen

Published in: LIPIcs, Volume 337, 10th International Conference on Formal Structures for Computation and Deduction (FSCD 2025)

Abstract
We look at the generalization problem modulo some equational theories. This problem is dual to the unification problem: given two input terms, we want to find a common term whose respective two instances are equivalent to the original terms modulo the theory. There exist algorithms for finding generalizations over various equational theories. We focus on modular construction of equational generalization algorithms for the union of signature-disjoint theories. Specifically, we consider the class of regular and collapse-free theories, showing how to combine existing generalization algorithms to produce specific solutions in these cases. Additionally, we identify a class of theories that admit a generalization algorithm based on the application of axioms to resolve the problem. To define this class, we rely on the notion of syntactic theories, a concept originally introduced to develop unification procedures similar to the one known for syntactic unification. We demonstrate that syntactic theories are also helpful in developing generalization procedures similar to those used for syntactic generalization.
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Mauricio Ayala-Rincón, David M. Cerna, Temur Kutsia, and Christophe Ringeissen. Combining Generalization Algorithms in Regular Collapse-Free Theories. In 10th International Conference on Formal Structures for Computation and Deduction (FSCD 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 337, pp. 7:1-7:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{ayalarincon_et_al:LIPIcs.FSCD.2025.7,
  author =	{Ayala-Rinc\'{o}n, Mauricio and Cerna, David M. and Kutsia, Temur and Ringeissen, Christophe},
  title =	{{Combining Generalization Algorithms in Regular Collapse-Free Theories}},
  booktitle =	{10th International Conference on Formal Structures for Computation and Deduction (FSCD 2025)},
  pages =	{7:1--7:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-374-4},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{337},
  editor =	{Fern\'{a}ndez, Maribel},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSCD.2025.7},
  URN =		{urn:nbn:de:0030-drops-236228},
  doi =		{10.4230/LIPIcs.FSCD.2025.7},
  annote =	{Keywords: Generalization, Anti-unification, Equational theories, Combination}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2024.25
Compositional Symbolic Execution for Correctness and Incorrectness Reasoning

Authors: Andreas Lööw, Daniele Nantes-Sobrinho, Sacha-Élie Ayoun, Caroline Cronjäger, Petar Maksimović, and Philippa Gardner

Published in: LIPIcs, Volume 313, 38th European Conference on Object-Oriented Programming (ECOOP 2024)

Abstract
The introduction of separation logic has led to the development of symbolic execution techniques and tools that are (functionally) compositional with function specifications that can be used in broader calling contexts. Many of the compositional symbolic execution tools developed in academia and industry have been grounded on a formal foundation, but either the function specifications are not validated with respect to the underlying separation logic of the theory, or there is a large gulf between the theory and the implementation of the tool. We introduce a formal compositional symbolic execution engine which creates and uses function specifications from an underlying separation logic and provides a sound theoretical foundation for, and indeed was partially inspired by, the Gillian symbolic execution platform. This is achieved by providing an axiomatic interface which describes the properties of the consume and produce operations used in the engine to update compositionally the symbolic state, for example when calling function specifications. This consume-produce technique is used by VeriFast, Viper, and Gillian, but has not been previously characterised independently of the tool. As part of our result, we give consume and produce operations inspired by the Gillian implementation that satisfy the properties described by our axiomatic interface. A surprising property is that our engine semantics provides a common foundation for both correctness and incorrectness reasoning, with the difference in the underlying engine only amounting to the choice to use satisfiability or validity. We use this property to extend the Gillian platform, which previously only supported correctness reasoning, with incorrectness reasoning and automatic true bug-finding using incorrectness bi-abduction. We evaluate our new Gillian platform by using the Gillian instantiation to C. This instantiation is the first tool grounded on a common formal compositional symbolic execution engine to support both correctness and incorrectness reasoning.
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Andreas Lööw, Daniele Nantes-Sobrinho, Sacha-Élie Ayoun, Caroline Cronjäger, Petar Maksimović, and Philippa Gardner. Compositional Symbolic Execution for Correctness and Incorrectness Reasoning. In 38th European Conference on Object-Oriented Programming (ECOOP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 313, pp. 25:1-25:28, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{loow_et_al:LIPIcs.ECOOP.2024.25,
  author =	{L\"{o}\"{o}w, Andreas and Nantes-Sobrinho, Daniele and Ayoun, Sacha-\'{E}lie and Cronj\"{a}ger, Caroline and Maksimovi\'{c}, Petar and Gardner, Philippa},
  title =	{{Compositional Symbolic Execution for Correctness and Incorrectness Reasoning}},
  booktitle =	{38th European Conference on Object-Oriented Programming (ECOOP 2024)},
  pages =	{25:1--25:28},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-341-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{313},
  editor =	{Aldrich, Jonathan 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.2024.25},
  URN =		{urn:nbn:de:0030-drops-208741},
  doi =		{10.4230/LIPIcs.ECOOP.2024.25},
  annote =	{Keywords: separation logic, incorrectness logic, symbolic execution, bi-abduction}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2024.26
Matching Plans for Frame Inference in Compositional Reasoning

Authors: Andreas Lööw, Daniele Nantes-Sobrinho, Sacha-Élie Ayoun, Petar Maksimović, and Philippa Gardner

Published in: LIPIcs, Volume 313, 38th European Conference on Object-Oriented Programming (ECOOP 2024)

Abstract
The use of function specifications to reason about function calls and the manipulation of user-defined predicates are two essential ingredients of modern compositional verification tools based on separation logic. To execute these operations successfully, these tools must be able to solve the frame inference problem, that is, to understand which parts of the state are relevant for the operation at hand. We introduce matching plans, a concept that is used in the Gillian verification platform to automate frame inference efficiently. We extract matching plans and their automation machinery from the Gillian implementation and present them in a tool-agnostic way, making the Gillian approach available to the broader verification community as a verification-tool design pattern.
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Andreas Lööw, Daniele Nantes-Sobrinho, Sacha-Élie Ayoun, Petar Maksimović, and Philippa Gardner. Matching Plans for Frame Inference in Compositional Reasoning. In 38th European Conference on Object-Oriented Programming (ECOOP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 313, pp. 26:1-26:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{loow_et_al:LIPIcs.ECOOP.2024.26,
  author =	{L\"{o}\"{o}w, Andreas and Nantes-Sobrinho, Daniele and Ayoun, Sacha-\'{E}lie and Maksimovi\'{c}, Petar and Gardner, Philippa},
  title =	{{Matching Plans for Frame Inference in Compositional Reasoning}},
  booktitle =	{38th European Conference on Object-Oriented Programming (ECOOP 2024)},
  pages =	{26:1--26:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-341-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{313},
  editor =	{Aldrich, Jonathan 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.2024.26},
  URN =		{urn:nbn:de:0030-drops-208751},
  doi =		{10.4230/LIPIcs.ECOOP.2024.26},
  annote =	{Keywords: Compositional reasoning, separation logic, frame inference}
}
Document
Artifact
DOI: 10.4230/DARTS.10.2.13
Compositional Symbolic Execution for Correctness and Incorrectness Reasoning (Artifact)

Authors: Andreas Lööw, Daniele Nantes-Sobrinho, Sacha-Élie Ayoun, Caroline Cronjäger, Nat Karmios, Petar Maksimović, and Philippa Gardner

Published in: DARTS, Volume 10, Issue 2, Special Issue of the 38th European Conference on Object-Oriented Programming (ECOOP 2024)

Abstract
This artifact is a companion to the paper "Compositional Symbolic Execution for Correctness and Incorrectness Reasoning". It contains the source code of the Gillian compositional symbolic execution (CSE) platform, in which we added the incorrectness reasoning capabilities, and the benchmarks used in the evaluation of the paper. It also contains a Haskell demonstrator CSE engine that directly implements the CSE engine inference rules presented in the paper.
Cite as

Andreas Lööw, Daniele Nantes-Sobrinho, Sacha-Élie Ayoun, Caroline Cronjäger, Nat Karmios, Petar Maksimović, and Philippa Gardner. Compositional Symbolic Execution for Correctness and Incorrectness Reasoning (Artifact). In Special Issue of the 38th European Conference on Object-Oriented Programming (ECOOP 2024). Dagstuhl Artifacts Series (DARTS), Volume 10, Issue 2, pp. 13:1-13:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@Article{loow_et_al:DARTS.10.2.13,
  author =	{L\"{o}\"{o}w, Andreas and Nantes-Sobrinho, Daniele and Ayoun, Sacha-\'{E}lie and Cronj\"{a}ger, Caroline and Karmios, Nat and Maksimovi\'{c}, Petar and Gardner, Philippa},
  title =	{{Compositional Symbolic Execution for Correctness and Incorrectness Reasoning (Artifact)}},
  pages =	{13:1--13:2},
  journal =	{Dagstuhl Artifacts Series},
  ISBN =	{978-3-95977-342-3},
  ISSN =	{2509-8195},
  year =	{2024},
  volume =	{10},
  number =	{2},
  editor =	{L\"{o}\"{o}w, Andreas and Nantes-Sobrinho, Daniele and Ayoun, Sacha-\'{E}lie and Cronj\"{a}ger, Caroline and Karmios, Nat and Maksimovi\'{c}, Petar and Gardner, Philippa},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DARTS.10.2.13},
  URN =		{urn:nbn:de:0030-drops-209110},
  doi =		{10.4230/DARTS.10.2.13},
  annote =	{Keywords: separation logic, incorrectness logic, symbolic execution, bi-abduction}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2023.19
Exact Separation Logic: Towards Bridging the Gap Between Verification and Bug-Finding

Authors: Petar Maksimović, Caroline Cronjäger, Andreas Lööw, Julian Sutherland, and Philippa Gardner

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

Abstract
Over-approximating (OX) program logics, such as separation logic (SL), are used for verifying properties of heap-manipulating programs: all terminating behaviour is characterised, but established results and errors need not be reachable. OX function specifications are thus incompatible with true bug-finding supported by symbolic execution tools such as Pulse and Pulse-X. In contrast, under-approximating (UX) program logics, such as incorrectness separation logic, are used to find true results and bugs: established results and errors are reachable, but there is no mechanism for understanding if all terminating behaviour has been characterised. We introduce exact separation logic (ESL), which provides fully-verified function specifications compatible with both OX verification and UX true bug-funding: all terminating behaviour is characterised and all established results and errors are reachable. We prove soundness for ESL with mutually recursive functions, demonstrating, for the first time, function compositionality for a UX logic. We show that UX program logics require subtle definitions of internal and external function specifications compared with the familiar definitions of OX logics. We investigate the expressivity of ESL and, for the first time, explore the role of abstraction in UX reasoning by verifying abstract ESL specifications of various data-structure algorithms. In doing so, we highlight the difference between abstraction (hiding information) and over-approximation (losing information). Our findings demonstrate that abstraction cannot be used as freely in UX logics as in OX logics, but also that it should be feasible to use ESL to provide tractable function specifications for self-contained, critical code, which would then be used for both verification and true bug-finding.
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Petar Maksimović, Caroline Cronjäger, Andreas Lööw, Julian Sutherland, and Philippa Gardner. Exact Separation Logic: Towards Bridging the Gap Between Verification and Bug-Finding. In 37th European Conference on Object-Oriented Programming (ECOOP 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 263, pp. 19:1-19:27, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{maksimovic_et_al:LIPIcs.ECOOP.2023.19,
  author =	{Maksimovi\'{c}, Petar and Cronj\"{a}ger, Caroline and L\"{o}\"{o}w, Andreas and Sutherland, Julian and Gardner, Philippa},
  title =	{{Exact Separation Logic: Towards Bridging the Gap Between Verification and Bug-Finding}},
  booktitle =	{37th European Conference on Object-Oriented Programming (ECOOP 2023)},
  pages =	{19:1--19:27},
  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.2023.19},
  URN =		{urn:nbn:de:0030-drops-182123},
  doi =		{10.4230/LIPIcs.ECOOP.2023.19},
  annote =	{Keywords: Separation logic, program correctness, program incorrectness, abstraction}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.CONCUR.2022.2
Concurrent Separation Logics: Logical Abstraction, Logical Atomicity and Environment Liveness Conditions (Invited Talk)

Authors: Philippa Gardner

Published in: LIPIcs, Volume 243, 33rd International Conference on Concurrency Theory (CONCUR 2022)

Abstract
Scalable verification for concurrent programs with shared memory is a long-standing, difficult problem. In 2004, O'Hearn and Brookes introduced concurrent separation logic to provide compositional reasoning about coarse-grained concurrent programs with synchronisation primitives (Gödel prize, 2016). In 2010, I introduced logical abstraction (the fiction of separation) to CSL, developing the CAP logic for reasoning about fine-grained concurrent programs in general and fine-grained lock algorithms in particular. In one logic, it was possible to provide two-sided specifications of concurrent operations, with formally verified implementations and clients. In 2014, I introduced logical atomicity (the fiction of atomicity) to concurrent separation logics, developing the TaDA logic to capture when individual operations behave atomically. Unlike CAP, where synchronisation primitives leak into the specifications, with TaDA the specifications are "just right" in that they provide more general atomic functions specifications to capture, for example, the full behaviour of lock operations. In 2021, I introduced environment liveness conditions to concurrent separation logics, developing the TaDA Live logic for reasoning compositionally about the termination of blocking fine-grained concurrent programs. The crucial challenge is how to deal with abstract atomic blocking: that is, abstract atomic operations that have blocking behaviour arising from busy-waiting patterns as found in, for example, fine-grained spin locks. The fundamental innovation is with the design of abstract specifications that capture this blocking behaviour as liveness assumptions on the environment. In this talk, I will explain this on-going journey in the wonderful world of concurrent separation logics. I will also explain why I have a bright green office chair in the corner of my office, patterned in gold lamé. Many thanks to my fabulous coauthors on concurrent separation logics: Thomas Dinsdale-Young, Emanuele D'Osualdo, Mike Dodds, Azadeh Farzan, Matthew Parkinson, Pedro da Rocha Pinto, Julian Sutherland, Viktor Vafeiadis and more. Suggested Reading: - Peter O'Hearn: Resources, Concurrency and Local Reasoning, Journal of Theoretical Computer Science, Festschrift for John C Reynolds 70th birthday, 2007. - Thomas Dinsdale-Young, Pedro da Rocha Pinto and Philippa Gardner: A Perspective on Specifying and Verifying Concurrent Modules, Journal of Logical and Algebraic Methods in Programming, 2018. - Emanuele D'Osualdo, Azadeh Farzan, Philippa Gardner and Julian Sutherland: TaDA Live: Compositional Reasoning for Termination of Fine-grained Concurrent Programs, ACM Transactions on Programming Languages and Systems (TOPLAS), 2021.
Cite as

Philippa Gardner. Concurrent Separation Logics: Logical Abstraction, Logical Atomicity and Environment Liveness Conditions (Invited Talk). In 33rd International Conference on Concurrency Theory (CONCUR 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 243, p. 2:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{gardner:LIPIcs.CONCUR.2022.2,
  author =	{Gardner, Philippa},
  title =	{{Concurrent Separation Logics: Logical Abstraction, Logical Atomicity and Environment Liveness Conditions}},
  booktitle =	{33rd International Conference on Concurrency Theory (CONCUR 2022)},
  pages =	{2:1--2:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-246-4},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{243},
  editor =	{Klin, Bartek and Lasota, S{\l}awomir and Muscholl, Anca},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2022.2},
  URN =		{urn:nbn:de:0030-drops-170659},
  doi =		{10.4230/LIPIcs.CONCUR.2022.2},
  annote =	{Keywords: Concurrent separation logic}
}
Document
Artifact
DOI: 10.4230/DARTS.6.2.5
A Trusted Infrastructure for Symbolic Analysis of Event-Driven Web Applications (Artifact)

Authors: Gabriela Sampaio, José Fragoso Santos, Petar Maksimović, and Philippa Gardner

Published in: DARTS, Volume 6, Issue 2, Special Issue of the 34th European Conference on Object-Oriented Programming (ECOOP 2020)

Abstract
This artifact contains the implementation of JaVerT.Click, a symbolic analysis tool for modern event-driven Web applications. The tool extends JaVerT 2.0, a state-of-the-art symbolic execution tool for JavaScript (JS), with JS reference implementations of the DOM Core Level 1, DOM UI Events, JavaScript Promises and the JavaScript async/await APIs, all underpinned by a simple Core Event Semantics which is sufficiently expressive to describe the event models underlying these APIs. Our reference implementations mostly follow the respective standards line-by-line and are all thoroughly tested against the official test suite. We also evaluate JaVerT.Click by performing symbolic analysis on two real-world libraries: cash and p-map, finding three previously unknown bugs.
Cite as

Gabriela Sampaio, José Fragoso Santos, Petar Maksimović, and Philippa Gardner. A Trusted Infrastructure for Symbolic Analysis of Event-Driven Web Applications (Artifact). In Special Issue of the 34th European Conference on Object-Oriented Programming (ECOOP 2020). Dagstuhl Artifacts Series (DARTS), Volume 6, Issue 2, pp. 5:1-5:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@Article{sampaio_et_al:DARTS.6.2.5,
  author =	{Sampaio, Gabriela and Fragoso Santos, Jos\'{e} and Maksimovi\'{c}, Petar and Gardner, Philippa},
  title =	{{A Trusted Infrastructure for Symbolic Analysis of Event-Driven Web Applications (Artifact)}},
  pages =	{5:1--5:3},
  journal =	{Dagstuhl Artifacts Series},
  ISSN =	{2509-8195},
  year =	{2020},
  volume =	{6},
  number =	{2},
  editor =	{Sampaio, Gabriela and Fragoso Santos, Jos\'{e} and Maksimovi\'{c}, Petar and Gardner, Philippa},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DARTS.6.2.5},
  URN =		{urn:nbn:de:0030-drops-132028},
  doi =		{10.4230/DARTS.6.2.5},
  annote =	{Keywords: Events, DOM, JavaScript, promises, symbolic execution, bug-finding}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2020.21
Data Consistency in Transactional Storage Systems: A Centralised Semantics

Authors: Shale Xiong, Andrea Cerone, Azalea Raad, and Philippa Gardner

Published in: LIPIcs, Volume 166, 34th European Conference on Object-Oriented Programming (ECOOP 2020)

Abstract
We introduce an interleaving operational semantics for describing the client-observable behaviour of atomic transactions on distributed key-value stores. Our semantics builds on abstract states comprising centralised, global key-value stores and partial client views. Using our abstract states, we present operational definitions of well-known consistency models in the literature, and prove them to be equivalent to their existing declarative definitions using abstract executions. We explore two applications of our operational framework: 1) verifying that the COPS replicated database and the Clock-SI partitioned database satisfy their consistency models using trace refinement, and 2) proving invariant properties of client programs.
Cite as

Shale Xiong, Andrea Cerone, Azalea Raad, and Philippa Gardner. Data Consistency in Transactional Storage Systems: A Centralised Semantics. In 34th European Conference on Object-Oriented Programming (ECOOP 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 166, pp. 21:1-21:31, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{xiong_et_al:LIPIcs.ECOOP.2020.21,
  author =	{Xiong, Shale and Cerone, Andrea and Raad, Azalea and Gardner, Philippa},
  title =	{{Data Consistency in Transactional Storage Systems: A Centralised Semantics}},
  booktitle =	{34th European Conference on Object-Oriented Programming (ECOOP 2020)},
  pages =	{21:1--21:31},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-154-2},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{166},
  editor =	{Hirschfeld, Robert and Pape, Tobias},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2020.21},
  URN =		{urn:nbn:de:0030-drops-131782},
  doi =		{10.4230/LIPIcs.ECOOP.2020.21},
  annote =	{Keywords: Operational Semantics, Consistency Models, Transactions, Distributed Key-value Stores}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2020.28
A Trusted Infrastructure for Symbolic Analysis of Event-Driven Web Applications

Authors: Gabriela Sampaio, José Fragoso Santos, Petar Maksimović, and Philippa Gardner

Published in: LIPIcs, Volume 166, 34th European Conference on Object-Oriented Programming (ECOOP 2020)

Abstract
We introduce a trusted infrastructure for the symbolic analysis of modern event-driven Web applications. This infrastructure consists of reference implementations of the DOM Core Level 1, DOM UI Events, JavaScript Promises and the JavaScript async/await APIs, all underpinned by a simple Core Event Semantics which is sufficiently expressive to describe the event models underlying these APIs. Our reference implementations are trustworthy in that three follow the appropriate standards line-by-line and all are thoroughly tested against the official test-suites, passing all the applicable tests. Using the Core Event Semantics and the reference implementations, we develop JaVerT.Click, a symbolic execution tool for JavaScript that, for the first time, supports reasoning about JavaScript programs that use multiple event-related APIs. We demonstrate the viability of JaVerT.Click by proving both the presence and absence of bugs in real-world JavaScript code.
Cite as

Gabriela Sampaio, José Fragoso Santos, Petar Maksimović, and Philippa Gardner. A Trusted Infrastructure for Symbolic Analysis of Event-Driven Web Applications. In 34th European Conference on Object-Oriented Programming (ECOOP 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 166, pp. 28:1-28:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{sampaio_et_al:LIPIcs.ECOOP.2020.28,
  author =	{Sampaio, Gabriela and Fragoso Santos, Jos\'{e} and Maksimovi\'{c}, Petar and Gardner, Philippa},
  title =	{{A Trusted Infrastructure for Symbolic Analysis of Event-Driven Web Applications}},
  booktitle =	{34th European Conference on Object-Oriented Programming (ECOOP 2020)},
  pages =	{28:1--28:29},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-154-2},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{166},
  editor =	{Hirschfeld, Robert and Pape, Tobias},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2020.28},
  URN =		{urn:nbn:de:0030-drops-131853},
  doi =		{10.4230/LIPIcs.ECOOP.2020.28},
  annote =	{Keywords: Events, DOM, JavaScript, promises, symbolic execution, bug-finding}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2019.9
A Program Logic for First-Order Encapsulated WebAssembly

Authors: Conrad Watt, Petar Maksimović, Neelakantan R. Krishnaswami, and Philippa Gardner

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

Abstract
We introduce Wasm Logic, a sound program logic for first-order, encapsulated WebAssembly. We design a novel assertion syntax, tailored to WebAssembly’s stack-based semantics and the strong guarantees given by WebAssembly’s type system, and show how to adapt the standard separation logic triple and proof rules in a principled way to capture WebAssembly’s uncommon structured control flow. Using Wasm Logic, we specify and verify a simple WebAssembly B-tree library, giving abstract specifications independent of the underlying implementation. We mechanise Wasm Logic and its soundness proof in full in Isabelle/HOL. As part of the soundness proof, we formalise and fully mechanise a novel, big-step semantics of WebAssembly, which we prove equivalent, up to transitive closure, to the original WebAssembly small-step semantics. Wasm Logic is the first program logic for WebAssembly, and represents a first step towards the creation of static analysis tools for WebAssembly.
Cite as

Conrad Watt, Petar Maksimović, Neelakantan R. Krishnaswami, and Philippa Gardner. A Program Logic for First-Order Encapsulated WebAssembly. In 33rd European Conference on Object-Oriented Programming (ECOOP 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 134, pp. 9:1-9:30, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{watt_et_al:LIPIcs.ECOOP.2019.9,
  author =	{Watt, Conrad and Maksimovi\'{c}, Petar and Krishnaswami, Neelakantan R. and Gardner, Philippa},
  title =	{{A Program Logic for First-Order Encapsulated WebAssembly}},
  booktitle =	{33rd European Conference on Object-Oriented Programming (ECOOP 2019)},
  pages =	{9:1--9:30},
  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.2019.9},
  URN =		{urn:nbn:de:0030-drops-108011},
  doi =		{10.4230/LIPIcs.ECOOP.2019.9},
  annote =	{Keywords: WebAssembly, program logic, separation logic, soundness, mechanisation}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2018.4
A Concurrent Specification of POSIX File Systems

Authors: Gian Ntzik, Pedro da Rocha Pinto, Julian Sutherland, and Philippa Gardner

Published in: LIPIcs, Volume 109, 32nd European Conference on Object-Oriented Programming (ECOOP 2018)

Abstract
POSIX is a standard for operating systems, with a substantial part devoted to specifying file-system operations. File-system operations exhibit complex concurrent behaviour, comprising multiple actions affecting different parts of the state: typically, multiple atomic reads followed by an atomic update. However, the standard's description of concurrent behaviour is unsatisfactory: it is fragmented; contains ambiguities; and is generally under-specified. We provide a formal concurrent specification of POSIX file systems and demonstrate scalable reasoning for clients. Our specification is based on a concurrent specification language, which uses a modern concurrent separation logic for reasoning about abstract atomic operations, and an associated refinement calculus. Our reasoning about clients highlights an important difference between reasoning about modules built over a heap, where the interference on the shared state is restricted to the operations of the module, and modules built over a file system, where the interference cannot be restricted as the file system is a public namespace. We introduce specifications conditional on context invariants used to restrict the interference, and apply our reasoning to the example of lock files.
Cite as

Gian Ntzik, Pedro da Rocha Pinto, Julian Sutherland, and Philippa Gardner. A Concurrent Specification of POSIX File Systems. In 32nd European Conference on Object-Oriented Programming (ECOOP 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 109, pp. 4:1-4:28, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{ntzik_et_al:LIPIcs.ECOOP.2018.4,
  author =	{Ntzik, Gian and da Rocha Pinto, Pedro and Sutherland, Julian and Gardner, Philippa},
  title =	{{A Concurrent Specification of POSIX File Systems}},
  booktitle =	{32nd European Conference on Object-Oriented Programming (ECOOP 2018)},
  pages =	{4:1--4:28},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-079-8},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{109},
  editor =	{Millstein, Todd},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2018.4},
  URN =		{urn:nbn:de:0030-drops-92092},
  doi =		{10.4230/LIPIcs.ECOOP.2018.4},
  annote =	{Keywords: POSIX, concurrency, file systems, refinement, separation logic, atomicity}
}
Document
DOI: 10.4230/DagRep.5.5.1
Compositional Verification Methods for Next-Generation Concurrency (Dagstuhl Seminar 15191)

Authors: Lars Birkedal, Derek Dreyer, Philippa Gardner, and Zhong Shao

Published in: Dagstuhl Reports, Volume 5, Issue 5 (2016)

Abstract
This report documents the program and the outcomes of Dagstuhl Seminar 15191 "Compositional Verification Methods for Next-Generation Concurrency". The seminar was successful and facilitated a stimulating interchange between the theory and practice of concurrent programming, and thereby laid the ground for the development of compositional verification methods that can scale to handle the realities of next-generation concurrency.
Cite as

Lars Birkedal, Derek Dreyer, Philippa Gardner, and Zhong Shao. Compositional Verification Methods for Next-Generation Concurrency (Dagstuhl Seminar 15191). In Dagstuhl Reports, Volume 5, Issue 5, pp. 1-23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)

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@Article{birkedal_et_al:DagRep.5.5.1,
  author =	{Birkedal, Lars and Dreyer, Derek and Gardner, Philippa and Shao, Zhong},
  title =	{{Compositional Verification Methods for Next-Generation Concurrency (Dagstuhl Seminar 15191)}},
  pages =	{1--23},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2015},
  volume =	{5},
  number =	{5},
  editor =	{Birkedal, Lars and Dreyer, Derek and Gardner, Philippa and Shao, Zhong},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.5.5.1},
  URN =		{urn:nbn:de:0030-drops-53565},
  doi =		{10.4230/DagRep.5.5.1},
  annote =	{Keywords: Verification of Concurrent Programs (Models, Logics, Automated Analysis), Concurrent Programming}
}
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