Causal Consistency for Reversible Multiparty Protocols

In programming models with a reversible semantics, computational steps can be undone. This paper addresses the integration of reversible semantics into process languages for communication-centric systems equipped with behavioral types. In prior work, we introduced a monitors-as-memories approach to seamlessly integrate reversible semantics into a process model in which concurrency is governed by session types (a class of behavioral types), covering binary (two-party) protocols with synchronous communication. The applicability and expressiveness of the binary setting, however, is limited. Here we extend our approach, and use it to define reversible semantics for an expressive process model that accounts for multiparty (n-party) protocols, asynchronous communication, decoupled rollbacks, and abstraction passing. As main result, we prove that our reversible semantics for multiparty protocols is causally-consistent. A key technical ingredient in our developments is an alternative reversible semantics with atomic rollbacks, which is conceptually simple and is shown to characterize decoupled rollbacks.Comment: Extended, revised version of a PPDP'17 paper (https://doi.org/10.1145/3131851.3131864

Cyberbullying, K-12 Public Schools, and the 1st Amendment

The first amendment protected students’ first amendment rights in K-12 public schools; however, state antibullying legislation required school officials to discipline students for bullying and, in most states, cyberbullying as well. An increasing number of students had access to mobile devices at home and during the school day. School officials had the responsibility to protect students from instances of bullying and cyberbullying; however, school officials did not fully understand the extent of their authority to discipline students for acts of bullying that occurred online, off school grounds. Despite the existence of state antibullying laws in all fifty states, contradictory appellate court decisions in cases involving cyberbullying and K-12 public schools made it difficult for school administrators to understand their authority. Appellate courts utilized a Tinker test when determining the outcomes of cases involving cyberbullying and K-12 public schools. The Tinker test was derived from the Supreme Court decision in Tinker vs. Des Moines Independent Community School District (1969), in which the Supreme Court overturned the suspension of students that wore armbands to protest the Vietnam War. There were two prongs of the Tinker test: (1) whether the instance of cyberbullying caused a substantial interference in the school, and (2) whether or not a substantial interference could be reasonably forecasted. The purpose of this public policy dissertation was to provide state legislators and school administrators with an in-depth review of state antibullying laws as well as greater insight into how the appellate courts interpreted the extent and limitations of First Amendment in K-12 public schools. This public policy dissertation compared state antibullying legislation in all 50 states in the United States and reviews all appellate court decisions involving K-12 public schools and cyberbullying. Each state’s legislation was reviewed between October 31, 2016, and December 31, 2016, to determine (1) if there was an antibullying law in effect, (2) if cyberbullying was included in the legislation, (3) if bullying was defined as a one-time event, (4) if school officials were given the authority to discipline students for off-campus behavior, (5) if schools were required to implement an antibullying policy, (6) if the substantial interference or substantial disruption language from Tinker was included in the antibullying legislation, (7) if there was a school sanction for bullying, (8) if there was a criminal sanction for face-to-face bullying, and (9) if there was a criminal sanction for cyberbullying. Each appellate court decision involving K-12 public schools and cyberbullying was reviewed to determine how the Tinker test was applied in each case

Reversibility in session-based concurrency: A fresh look

Much research has studied foundations for correct and reliable communication-centric software systems. A salient approach to correctness uses verification based on session types to enforce structured communications; a recent approach to reliability uses reversible actions as a way of reacting to unanticipated events or failures. In this paper, we develop a simple observation: the semantic machinery required to define asynchronous (queue-based), monitored communications can also support reversible protocols. We propose a framework of session communication in which monitors support reversibility of (untyped) processes. Main novelty in our approach are session types with present and past, which allow us to streamline the semantics of reversible actions. We prove that reversibility in our framework is causally consistent, and define ways of using monitors to control reversible actions. Keyword

Bridging Causal Reversibility and Time Reversibility: A Stochastic Process Algebraic Approach

Causal reversibility blends reversibility and causality for concurrent systems. It indicates that an action can be undone provided that all of its consequences have been undone already, thus making it possible to bring the system back to a past consistent state. Time reversibility is instead considered in the field of stochastic processes, mostly for efficient analysis purposes. A performance model based on a continuous-time Markov chain is time reversible if its stochastic behavior remains the same when the direction of time is reversed. We bridge these two theories of reversibility by showing the conditions under which causal reversibility and time reversibility are both ensured by construction. This is done in the setting of a stochastic process calculus, which is then equipped with a variant of stochastic bisimilarity accounting for both forward and backward directions

Static versus dynamic reversibility in CCS

The notion of reversible computing is attracting interest because of its applications in diverse fields, in particular the study of programming abstractions for fault tolerant systems. Most computational models are not naturally reversible since computation causes loss of information, and history information must be stored to enable reversibility. In the literature, two approaches to reverse the CCS process calculus exist, differing on how history information is kept. Reversible CCS (RCCS), proposed by Danos and Krivine, exploits dedicated stacks of memories attached to each thread. CCS with Keys (CCSK), proposed by Phillips and Ulidowski, makes CCS operators static so that computation does not cause information loss. In this paper we show that RCCS and CCSK are equivalent in terms of LTS isomorphism

Categorization of phraseological units: Russian/Italian expressions

Marabini, A. Categorization of phraseological units: Russian/Italian expressions / A. Marabini, A. A. Mezzina // Научный результат. Сер. Вопросы теоретической и прикладной лингвистики. - 2020. - Vol.6, N3.-P. 58-71. - Doi: 10.18413/2313-8912-2020-6-3-0-5. - Refer.: p. 69-71.The current article takes into consideration the typology proposed by the Italian linguist Federica Casadei, which will serve as a basis for the authors’ categorization of specific Russian expressions. The purpose of this paper is to illustrate the full and partial correspondence of Italian and Russian phraseological units through a new schematizatio

The Reversible Temporal Process Language

Reversible debuggers help programmers to quickly find the causes of misbehaviours in concurrent programs. These debuggers can be founded on the well-studied theory of causal-consistent reversibility, which allows one to undo any action provided that its consequences are undone beforehand. Till now, causal-consistent reversibility never considered time, a key aspect in real world applications. Here, we study the interplay between reversibility and time in concurrent systems via a process algebra. The Temporal Process Language (TPL) by Hennessy and Regan is a well-understood extension of CCS with discrete-time and a timeout operator. We define revTPL, a reversible extension of TPL, and we show that it satisfies the properties expected from a causal-consistent reversible calculus. We show that, alternatively, revTPL can be interpreted as an extension of reversible CCS with time

Bridging Causal Reversibility and Time Reversibility: A Stochastic Process Algebraic Approach

Causal reversibility blends reversibility and causality for concurrent systems. It indicates that an action can be undone provided that all of its consequences have been undone already, thus making it possible to bring the system back to a past consistent state. Time reversibility is instead considered in the field of stochastic processes, mostly for efficient analysis purposes. A performance model based on a continuous-time Markov chain is time reversible if its stochastic behavior remains the same when the direction of time is reversed. We bridge these two theories of reversibility by showing the conditions under which causal reversibility and time reversibility are both ensured by construction. This is done in the setting of a stochastic process calculus, which is then equipped with a variant of stochastic bisimilarity accounting for both forward and backward directions

Causally consistent reversible choreographies: a monitors-as-memories approach

Under a reversible semantics, computation steps can be undone. This paper addresses the integration of reversible semantics into a process model of multiparty protocols (choreographies). Building upon the monitors-as-memories approach that we developed in prior work for reversible binary protocols, we present a reversible process framework for multiparty communication, which improves on prior models by seamlessly integrating asynchrony, decoupled rollbacks, and process passing. As main technical result, we prove that our multiparty, reversible semantics is causally-consistent