arXiv subjects

Jorge A. Pérez

Publications and source records attributed to Jorge A. Pérez.

At least 19 recordsLinked to original sources

arXiv2026

Deadlock-free Context-free Session Types

We tackle the problem of statically ensuring that message-passing programs never run into deadlocks. We focus on concurrent functional programs governed by context-free session types, which can express rich tree-like structures not expressible in standard session types. We propose a new type system based on context-free session types: it enforces both protocol conformance and deadlock freedom, also for programs implementing cyclic communication topologies with recursion and polymorphism. We show how the priority-based approach to deadlock freedom can be extended to this expressive setting. We prove that well-typed concurrent programs respect their protocols and never deadlock.

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arXiv2025

A Minimal Formulation of Session Types: The Sessions of Trios in Concert

Session types are a type-based approach to the verification of message-passing programs. They specify communication structures essential to enforcing program correctness; by relying on sequencing constructs, a session type can precisely describe the intended order of communication actions through a channel. In this paper we study a fragment of session types that makes a very limited use of sequencing; we call it minimal session types. In the context of a core process calculus with sessions and higher-order concurrency, we establish two technical results. First, we prove that every process P typable with standard session types can be compiled down into a process D(P) typable with minimal session types. Second, we prove that P and D(P) are behaviorally equivalent. These results show that having sequencing in both processes and session types is convenient, but that only sequencing in processes is truly indispensable, as it can correctly codify sequencing in types. Our developments draw inspiration from work by Parrow on behavior-preserving decompositions of untyped processes using trios, i.e., processes with exactly three nested prefixes. By casting Parrow's approach in the realm of typed processes, our developments reveal a conceptually simple formulation of session types, supported by static and dynamic correctness results.

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arXiv2025

Contrasting Deadlock-Free Session Processes (Extended Version)

Deadlock freedom is a crucial property for message-passing programs. Over the years, several different type systems for concurrent processes that ensure deadlock freedom have been proposed; this diversity raises the question of how they compare. We address this question, considering two type systems not covered in prior work: Kokke etal's HCP, a type system based on a linear logic with hypersequents, and Padovani's priority-based type system for asynchronous processes, dubbed P. Their distinctive features make formal comparisons relevant and challenging. Our findings are two-fold: (1) the hypersequent setting does not drastically change the class of deadlock-free processes induced by linear logic, and (2) we relate the classes of deadlock-free processes induced by HCP and P. We prove that our results hold under both synchronous and asynchronous communication. Our results provide new insights into the essential mechanisms involved in statically avoiding deadlocks in concurrency.

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arXiv2024

A Gentle Overview of Asynchronous Session-based Concurrency: Deadlock Freedom by Typing

While formal models of concurrency tend to focus on synchronous communication, asynchronous communication is relevant in practice. In this paper, we will discuss asynchronous communication in the context of session-based concurrency, the model of computation in which session types specify the structure of the two-party protocols implemented by the channels of a communicating process. We overview recent work on addressing the challenge of ensuring the deadlock-freedom property for message-passing processes that communicate asynchronously in cyclic process networks governed by session types. We offer a gradual presentation of three typed process frameworks and outline how they may be used to guarantee deadlock freedom for a concurrent functional language with sessions.

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arXiv2024

Typed Non-determinism in Concurrent Calculi: The Eager Way

We consider the problem of designing typed concurrent calculi with non-deterministic choice in which types leverage linearity for controlling resources, thereby ensuring strong correctness properties for processes. This problem is constrained by the delicate tension between non-determinism and linearity. Prior work developed a session-typed π-calculus with standard non-deterministic choice; well-typed processes enjoy type preservation and deadlock-freedom. Central to this typed calculus is a lazy semantics that gradually discards branches in choices. This lazy semantics, however, is complex: various technical elements are needed to describe the non-deterministic behavior of typed processes. This paper develops an entirely new approach, based on an eager semantics, which more directly represents choices and commitment. We present a π-calculus in which non-deterministic choices are governed by this eager semantics and session types. We establish its key correctness properties, including deadlock-freedom, and demonstrate its expressivity by correctly translating a typed resource λ-calculus.

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arXiv2024

Asynchronous Session-Based Concurrency: Deadlock-freedom in Cyclic Process Networks

We tackle the challenge of ensuring the deadlock-freedom property for message-passing processes that communicate asynchronously in cyclic process networks. Our contributions are twofold. First, we present Asynchronous Priority-based Classical Processes (APCP), a session-typed process framework that supports asynchronous communication, delegation, and recursion in cyclic process networks. Building upon the Curry-Howard correspondences between linear logic and session types, we establish essential meta-theoretical results for APCP, most notably deadlock freedom. Second, we present a new concurrent $λ$-calculus with asynchronous session types, dubbed LASTn. We illustrate LASTn by example and establish its meta-theoretical results; in particular, we show how to soundly transfer the deadlock-freedom guarantee from APCP. To this end, we develop a translation of terms in LASTn into processes in APCP that satisfies a strong formulation of operational correspondence.

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arXiv2024

Comparing Session Type Systems derived from Linear Logic

Session types are a typed approach to message-passing concurrency, where types describe sequences of intended exchanges over channels. Session type systems have been given strong logical foundations via Curry-Howard correspondences with linear logic, a resource-aware logic that naturally captures structured interactions. These logical foundations provide an elegant framework to specify and (statically) verify message-passing processes. In this paper, we rigorously compare different type systems for concurrency derived from the Curry-Howard correspondence between linear logic and session types. We address the main divide between these type systems: the classical and intuitionistic presentations of linear logic. Over the years, these presentations have given rise to separate research strands on logical foundations for concurrency; the differences between their derived type systems have only been addressed informally. To formally assess these differences, we develop $π\mathsf{ULL}$, a session type system that encompasses type systems derived from classical and intuitionistic interpretations of linear logic. Based on a fragment of Girard's Logic of Unity, $π\mathsf{ULL}$ provides a basic reference framework: we compare existing session type systems by characterizing fragments of $π\mathsf{ULL}$ that coincide with classical and intuitionistic formulations. We analyze the significance of our characterizations by considering the locality principle (enforced by intuitionistic interpretations but not by classical ones) and forms of process composition induced by the interpretations.

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arXiv2024

Around Classical and Intuitionistic Linear Processes

Curry-Howard correspondences between Linear Logic (LL) and session types provide a firm foundation for concurrent processes. As the correspondences hold for intuitionistic and classic versions of LL (ILL and CLL), we obtain two different families of type systems for concurrency. An open question remains: how do these two families exactly relate to each other? Based upon a translation from CLL to ILL due to Laurent (2018), we provide two complementary answers, in the form of full abstraction results based on a typed observational equivalence due to Atkey (2017). Our results elucidate hitherto missing formal links between seemingly related yet different type systems for concurrency.

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arXiv2024

Minimal Session Types for the $π$-calculus (Extended Version)

Session types are a discipline for the static verification of message-passing programs. A session type specifies a channel's protocol as sequences of exchanges. It is most relevant to investigate session-based concurrency by identifying the essential notions that enable program specification and verification. Following that perspective, prior work identified minimal session types (MSTs), a sub-class of session types without the sequentiality construct, which specifies the structure of communication actions. This formulation of session types led to establish a minimality result: every process typable with standard session types can be compiled down to a process typable using MSTs, which mimics sequentiality in types via additional process synchronizations. Such a minimality result is significant because it justifies session types in terms of themselves, without resorting to external notions; it was proven for a higher-order session pi-calculus, in which values are abstractions (functions from names to processes). In this paper, we study MSTs and their associated minimality result but now for the session pi-calculus, the (first-order) language in which values are names and for which session types have been more widely studied. We first show that this new minimality result can be obtained by composing known results. Then, we develop optimizations of this new minimality result and prove that the associated transformation into processes with MSTs satisfies dynamic correctness.

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arXiv2023

Non-Deterministic Functions as Non-Deterministic Processes (Extended Version)

We study encodings of the lambda-calculus into the pi-calculus in the unexplored case of calculi with non-determinism and failures. On the sequential side, we consider lambdafail, a new non-deterministic calculus in which intersection types control resources (terms); on the concurrent side, we consider spi, a pi-calculus in which non-determinism and failure rest upon a Curry-Howard correspondence between linear logic and session types. We present a typed encoding of lambdafail into spi and establish its correctness. Our encoding precisely explains the interplay of non-deterministic and fail-prone evaluation in lambdafail via typed processes in spi. In particular, it shows how failures in sequential evaluation (absence/excess of resources) can be neatly codified as interaction protocols.

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arXiv2023

Monitoring Blackbox Implementations of Multiparty Session Protocols

We present a framework for the distributed monitoring of networks of components that coordinate by message-passing, following multiparty session protocols specified as global types. We improve over prior works by (i) supporting components whose exact specification is unknown ("blackboxes") and (ii) covering protocols that cannot be analyzed by existing techniques. We first give a procedure for synthesizing monitors for blackboxes from global types, and precisely define when a blackbox correctly satisfies its global type. Then, we prove that monitored blackboxes are sound (they correctly follow the protocol) and transparent (blackboxes with and without monitors are behaviorally equivalent).

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arXiv2023

Typed Non-determinism in Functional and Concurrent Calculi

We study functional and concurrent calculi with non-determinism, along with type systems to control resources based on linearity. The interplay between non-determinism and linearity is delicate: careless handling of branches can discard resources meant to be used exactly once. Here we go beyond prior work by considering non-determinism in its standard sense: once a branch is selected, the rest are discarded. Our technical contributions are three-fold. First, we introduce a $π$-calculus with non-deterministic choice, governed by session types. Second, we introduce a resource $λ$-calculus, governed by intersection types, in which non-determinism concerns fetching of resources from bags. Finally, we connect our two typed non-deterministic calculi via a correct translation.

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arXiv2023

Termination in Concurrency, Revisited

Termination is a central property in sequential programming models: a term is terminating if all its reduction sequences are finite. Termination is also important in concurrency in general, and for message-passing programs in particular. A variety of type systems that enforce termination by typing have been developed. In this paper, we rigorously compare several type systems for $π$-calculus processes from the unifying perspective of termination. Adopting session types as reference framework, we consider two different type systems: one follows Deng and Sangiorgi's weight-based approach; the other is Caires and Pfenning's Curry-Howard correspondence between linear logic and session types. Our technical results precisely connect these very different type systems, and shed light on the classes of client/server interactions they admit as correct.

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arXiv2022

Asynchronous Functional Sessions: Cyclic and Concurrent (Extended Version)

We present Concurrent GV (CGV), a functional calculus with message-passing concurrency governed by session types. With respect to prior calculi, CGV has increased support for concurrent evaluation and for cyclic network topologies. The design of CGV draws on APCP, a session-typed asynchronous pi-calculus developed in prior work. Technical contributions are (i) the syntax, semantics, and type system of CGV; (ii) a correct translation of CGV into APCP; (iii) a technique for establishing deadlock-free CGV programs, by resorting to APCP's priority-based type system.

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arXiv2022

A Bunch of Sessions: A Propositions-as-Sessions Interpretation of Bunched Implications in Channel-Based Concurrency

The emergence of propositions-as-sessions, a Curry-Howard correspondence between propositions of Linear Logic and session types for concurrent processes, has settled the logical foundations of message-passing concurrency. Central to this approach is the resource consumption paradigm heralded by Linear Logic. In this paper, we investigate a new point in the design space of session type systems for message-passing concurrent programs. We identify O'Hearn and Pym's Logic of Bunched Implications (BI) as a fruitful basis for an interpretation of the logic as a concurrent programming language. This leads to a treatment of non-linear resources that is radically different from existing approaches based on Linear Logic. We introduce a new $π$-calculus with sessions, called $π$BI; its most salient feature is a construct called spawn, which expresses new forms of sharing that are induced by structural principles in BI. We illustrate the expressiveness of $π$BI and lay out its fundamental theory: type preservation, deadlock-freedom, and weak normalization results for well-typed processes; an operationally sound and complete typed encoding of an affine $λ$-calculus; and a non-interference result for access of resources.

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arXiv2022

Asynchronous Functional Sessions: Cyclic and Concurrent

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arXiv2022

Scalable Typestate Analysis for Low-Latency Environments

Static analyses based on typestates are important in certifying correctness of code contracts. Such analyses rely on Deterministic Finite Automata (DFAs) to specify properties of an object. We target the analysis of contracts in low-latency environments, where many useful contracts are impractical to codify as DFAs and/or the size of their associated DFAs leads to sub-par performance. To address this bottleneck, we present a lightweight typestate analyzer, based on an expressive specification language that can succinctly specify code contracts. By implementing it in the static analyzer Infer, we demonstrate considerable performance and usability benefits when compared to existing techniques. A central insight is to rely on a sub-class of DFAs with efficient bit-vector operations.

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arXiv2022

Types and Terms Translated: Unrestricted Resources in Encoding Functions as Processes (Extended Version)

Type-preserving translations are effective rigorous tools in the study of core programming calculi. In this paper, we develop a new typed translation that connects sequential and concurrent calculi; it is governed by type systems that control resource consumption. Our main contribution is the source language, a new resource $λ$-calculus with non-determinism and failures, dubbed \ulamf. In \ulamf, resources are split into linear and unrestricted; failures are explicit and arise from this distinction. We define a type system based on intersection types to control resources and fail-prone computation. The target language is \spi, an existing session-typed $π$-calculus that results from a Curry-Howard correspondence between linear logic and session types. Our typed translation subsumes our prior work; interestingly, it treats unrestricted resources in \lamrfailunres as client-server session behaviours in \spi.

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