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Invited Talk

DOI: 10.4230/LIPIcs.FSCD.2024.1

Meaningfulness and Genericity in a Subsuming Framework (Invited Talk)

Authors: Delia Kesner, Victor Arrial, and Giulio Guerrieri

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

Abstract

This paper studies the notion of meaningfulness for a unifying framework called dBang-calculus, which subsumes both call-by-name (dCBN) and call-by-value (dCBV). We first define meaningfulness in dBang and then characterize it by means of typability and inhabitation in an associated non-idempotent intersection type system previously appearing in the literature. We validate the proposed notion of meaningfulness by showing two properties: (1) consistency of the smallest theory, called ℋ, equating all meaningless terms, and (2) genericity, stating that meaningless subterms have no bearing on the significance of meaningful terms. The theory ℋ is also shown to have a unique consistent and maximal extension ℋ*, which coincides with a well-known notion of observational equivalence. Last but not least, we show that the notions of meaningfulness and genericity in the literature for dCBN and dCBV are subsumed by the corresponding ones proposed here for the dBang-calculus.

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Delia Kesner, Victor Arrial, and Giulio Guerrieri. Meaningfulness and Genericity in a Subsuming Framework (Invited Talk). In 9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 299, pp. 1:1-1:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{kesner_et_al:LIPIcs.FSCD.2024.1,
  author =	{Kesner, Delia and Arrial, Victor and Guerrieri, Giulio},
  title =	{{Meaningfulness and Genericity in a Subsuming Framework}},
  booktitle =	{9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024)},
  pages =	{1:1--1:24},
  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.2024.1},
  URN =		{urn:nbn:de:0030-drops-203305},
  doi =		{10.4230/LIPIcs.FSCD.2024.1},
  annote =	{Keywords: Lambda calculus, Solvability, Meaningfulness, Inhabitation, Genericity}
}

Document

DOI: 10.4230/LIPIcs.FSCD.2024.8

Mechanized Subject Expansion in Uniform Intersection Types for Perpetual Reductions

Authors: Andrej Dudenhefner and Daniele Pautasso

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

Abstract

We provide a new, purely syntactical proof of strong normalization for the simply typed λ-calculus. The result relies on a novel proof of the equivalence between typability in the simple type system and typability in the uniform intersection type system (a restriction of the non-idempotent intersection type system). For formal verification, the equivalence is mechanized using the Coq proof assistant. In the present work, strong normalization of a given simply typed term M is shown in four steps. First, M is reduced to a normal form N via a suitable reduction strategy with a decreasing measure. Second, a uniform intersection type for the normal form N is inferred. Third, a uniform intersection type for M is constructed iteratively via subject expansion. Fourth, strong normalization of M is shown by induction on the size of the type derivation. A supplementary contribution is a family of perpetual reduction strategies, i.e. strategies which preserve infinite reduction paths. This family allows for subject expansion in the intersection type systems of interest, and contains a reduction strategy with a decreasing measure in the simple type system. A notable member of this family is Barendregt’s F_∞ reduction strategy.

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Andrej Dudenhefner and Daniele Pautasso. Mechanized Subject Expansion in Uniform Intersection Types for Perpetual Reductions. In 9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 299, pp. 8:1-8:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{dudenhefner_et_al:LIPIcs.FSCD.2024.8,
  author =	{Dudenhefner, Andrej and Pautasso, Daniele},
  title =	{{Mechanized Subject Expansion in Uniform Intersection Types for Perpetual Reductions}},
  booktitle =	{9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024)},
  pages =	{8:1--8:20},
  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.2024.8},
  URN =		{urn:nbn:de:0030-drops-203371},
  doi =		{10.4230/LIPIcs.FSCD.2024.8},
  annote =	{Keywords: lambda-calculus, simple types, intersection types, strong normalization, mechanization, perpetual reductions}
}

Document

DOI: 10.4230/LIPIcs.FSCD.2024.11

Optimizing a Non-Deterministic Abstract Machine with Environments

Authors: Małgorzata Biernacka, Dariusz Biernacki, Sergueï Lenglet, and Alan Schmitt

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

Abstract

Non-deterministic abstract machine (NDAM) is a recent implementation model for programming languages where one must choose among several redexes at each reduction step, like process calculi. These machines can be derived from a zipper semantics, a mix between structural operational semantics and context-based reduction semantics. Such a machine has been generated also for the λ-calculus without a fixed reduction strategy, i.e., with the full non-deterministic β-reduction. In that machine, substitution is an external operation that replaces all the occurrences of a variable at once. Implementing substitution with environments is more low-level and more efficient as variables are replaced only when needed. In this paper, we define a NDAM with environments for the λ-calculus without a fixed reduction strategy. We also introduce other optimizations, including a form of refocusing, and we show that we can restrict our optimized NDAM to recover some of the usual λ-calculus machines, e.g., the Krivine Abstract Machine. Most of the improvements we propose in this work could be applied to other NDAMs as well.

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Małgorzata Biernacka, Dariusz Biernacki, Sergueï Lenglet, and Alan Schmitt. Optimizing a Non-Deterministic Abstract Machine with Environments. In 9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 299, pp. 11:1-11:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{biernacka_et_al:LIPIcs.FSCD.2024.11,
  author =	{Biernacka, Ma{\l}gorzata and Biernacki, Dariusz and Lenglet, Sergue\"{i} and Schmitt, Alan},
  title =	{{Optimizing a Non-Deterministic Abstract Machine with Environments}},
  booktitle =	{9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024)},
  pages =	{11:1--11:22},
  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.2024.11},
  URN =		{urn:nbn:de:0030-drops-203409},
  doi =		{10.4230/LIPIcs.FSCD.2024.11},
  annote =	{Keywords: Abstract machine, Explicit substitutions, Refocusing}
}

Document

DOI: 10.4230/LIPIcs.FSCD.2024.18

Representation of Peano Arithmetic in Separation Logic

Authors: Sohei Ito and Makoto Tatsuta

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

Abstract

Separation logic is successful for software verification of heap-manipulating programs. Numbers are necessary to be added to separation logic for verification of practical software where numbers are important. However, properties of the validity such as decidability and complexity for separation logic with numbers have not been fully studied yet. This paper presents the translation of Pi-0-1 formulas in Peano arithmetic to formulas in a small fragment of separation logic with numbers, which consists only of the intuitionistic points-to predicate, 0 and the successor function. Then this paper proves that a formula in Peano arithmetic is valid in the standard model if and only if its translation in this fragment is valid in the standard interpretation. As a corollary, this paper also gives a perspective proof for the undecidability of the validity in this fragment. Since Pi-0-1 formulas can describe consistency of logical systems and non-termination of computations, this result also shows that these properties discussed in Peano arithmetic can also be discussed in such a small fragment of separation logic with numbers.

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Sohei Ito and Makoto Tatsuta. Representation of Peano Arithmetic in Separation Logic. In 9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 299, pp. 18:1-18:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{ito_et_al:LIPIcs.FSCD.2024.18,
  author =	{Ito, Sohei and Tatsuta, Makoto},
  title =	{{Representation of Peano Arithmetic in Separation Logic}},
  booktitle =	{9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024)},
  pages =	{18:1--18:17},
  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.2024.18},
  URN =		{urn:nbn:de:0030-drops-203476},
  doi =		{10.4230/LIPIcs.FSCD.2024.18},
  annote =	{Keywords: First order logic, Separation logic, Peano arithmetic, Presburger arithmetic}
}

Document

DOI: 10.4230/LIPIcs.FSCD.2024.23

Mirroring Call-By-Need, or Values Acting Silly

Authors: Beniamino Accattoli and Adrienne Lancelot

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

Abstract

Call-by-need evaluation for the λ-calculus can be seen as merging the best of call-by-name and call-by-value, namely the wise erasing behaviour of the former and the wise duplicating behaviour of the latter. To better understand how duplication and erasure can be combined, we design a degenerated calculus, dubbed call-by-silly, that is symmetric to call-by-need in that it merges the worst of call-by-name and call-by-value, namely silly duplications by-name and silly erasures by-value. We validate the design of the call-by-silly calculus via rewriting properties and multi types. In particular, we mirror the main theorem about call-by-need - that is, its operational equivalence with call-by-name - showing that call-by-silly and call-by-value induce the same contextual equivalence. This fact shows the blindness with respect to efficiency of call-by-value contextual equivalence. We also define a call-by-silly strategy and measure its length via tight multi types. Lastly, we prove that the call-by-silly strategy computes evaluation sequences of maximal length in the calculus.

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Beniamino Accattoli and Adrienne Lancelot. Mirroring Call-By-Need, or Values Acting Silly. In 9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 299, pp. 23:1-23:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{accattoli_et_al:LIPIcs.FSCD.2024.23,
  author =	{Accattoli, Beniamino and Lancelot, Adrienne},
  title =	{{Mirroring Call-By-Need, or Values Acting Silly}},
  booktitle =	{9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024)},
  pages =	{23:1--23:24},
  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.2024.23},
  URN =		{urn:nbn:de:0030-drops-203527},
  doi =		{10.4230/LIPIcs.FSCD.2024.23},
  annote =	{Keywords: Lambda calculus, intersection types, call-by-value, call-by-need}
}

Document

DOI: 10.4230/LIPIcs.FSCD.2024.29

Böhm and Taylor for All!

Authors: Aloÿs Dufour and Damiano Mazza

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

Abstract

Böhm approximations, used in the definition of Böhm trees, are a staple of the semantics of the lambda-calculus. Introduced more recently by Ehrhard and Regnier, Taylor approximations provide a quantitative account of the behavior of programs and are well-known to be connected to intersection types. The key relation between these two notions of approximations is a commutation theorem, roughly stating that Taylor approximations of Böhm trees are the same as Böhm trees of Taylor approximations. Böhm and Taylor approximations are available for several variants or extensions of the lambda-calculus and, in some cases, commutation theorems are known. In this paper, we define Böhm and Taylor approximations and prove the commutation theorem in a very general setting. We also introduce (non-idempotent) intersection types at this level of generality. From this, we show how the commutation theorem and intersection types may be applied to any calculus embedding in a sufficiently nice way into our general calculus. All known Böhm-Taylor commutation theorems, as well as new ones, follow by this uniform construction.

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Aloÿs Dufour and Damiano Mazza. Böhm and Taylor for All!. In 9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 299, pp. 29:1-29:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{dufour_et_al:LIPIcs.FSCD.2024.29,
  author =	{Dufour, Alo\"{y}s and Mazza, Damiano},
  title =	{{B\"{o}hm and Taylor for All!}},
  booktitle =	{9th International Conference on Formal Structures for Computation and Deduction (FSCD 2024)},
  pages =	{29:1--29:20},
  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.2024.29},
  URN =		{urn:nbn:de:0030-drops-203582},
  doi =		{10.4230/LIPIcs.FSCD.2024.29},
  annote =	{Keywords: Linear logic, Differential linear logic, Taylor expansion of lambda-terms, B\"{o}hm trees, Process calculi}
}

Document

Track B: Automata, Logic, Semantics, and Theory of Programming

DOI: 10.4230/LIPIcs.ICALP.2024.136

Improved Algorithm for Reachability in d-VASS

Authors: Yuxi Fu, Qizhe Yang, and Yangluo Zheng

Published in: LIPIcs, Volume 297, 51st International Colloquium on Automata, Languages, and Programming (ICALP 2024)

Abstract

An 𝖥_{d} upper bound for the reachability problem in vector addition systems with states (VASS) in fixed dimension is given, where 𝖥_d is the d-th level of the Grzegorczyk hierarchy of complexity classes. The new algorithm combines the idea of the linear path scheme characterization of the reachability in the 2-dimension VASSes with the general decomposition algorithm by Mayr, Kosaraju and Lambert. The result improves the 𝖥_{d + 4} upper bound due to Leroux and Schmitz (LICS 2019).

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Yuxi Fu, Qizhe Yang, and Yangluo Zheng. Improved Algorithm for Reachability in d-VASS. In 51st International Colloquium on Automata, Languages, and Programming (ICALP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 297, pp. 136:1-136:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{fu_et_al:LIPIcs.ICALP.2024.136,
  author =	{Fu, Yuxi and Yang, Qizhe and Zheng, Yangluo},
  title =	{{Improved Algorithm for Reachability in d-VASS}},
  booktitle =	{51st International Colloquium on Automata, Languages, and Programming (ICALP 2024)},
  pages =	{136:1--136:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-322-5},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{297},
  editor =	{Bringmann, Karl and Grohe, Martin and Puppis, Gabriele and Svensson, Ola},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2024.136},
  URN =		{urn:nbn:de:0030-drops-202799},
  doi =		{10.4230/LIPIcs.ICALP.2024.136},
  annote =	{Keywords: Petri net, vector addition system, reachability}
}

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.

Cite as

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

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.

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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.

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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

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.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.

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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.

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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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