Guarded commands, nondeterminacy and formal derivation of programs

Dijkstra, Edsger W.

doi:10.1145/360933.360975

Cited by 1,511 publications

(483 citation statements)

References 2 publications

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“…The interval of execution of each b → idle is of finite length, i.e., b → idle must terminate. By (14), a guarded assignment to vector of variables b → y := e consists of two portions, where the guard and expressions e are evaluated in the first portion in the same apparent state, and y is updated to the new values in the second. Furthermore, execution of b → y := e ensures each output V not in y is stable and that each variable in V is right stable.…”

Section: Definition 5 (Action)mentioning

confidence: 99%

“…In particular, we calculate the effect of (partially) developed actions on the enforced properties, which generates new properties and actions. However, unlike [14,25,26], we disallow arbitrary modifications to the program. Instead, each change must be justified by a lemma/theorem that ensures each new version is a refinement of the current version [20,17].…”

Section: Action System Refinementmentioning

confidence: 99%

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Deriving real-time action systems with multiple time bands using algebraic reasoning

Dongol

Hayes

Derrick

2014

Science of Computer Programming

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The verify-while-develop paradigm allows one to incrementally develop programs from their specifications using a series of calculations against the remaining proof obligations. This paper presents a derivation method for real-time systems with realistic constraints on their behaviour. We develop a high-level intervalbased logic that provides flexibility in an implementation, yet allows algebraic reasoning over multiple granularities and sampling multiple sensors with delay. The semantics of an action system is given in terms of interval predicates and algebraic operators to unify the logics for an action system and its properties, which in turn simplifies the calculations and derivations.

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Section: Definition 5 (Action)mentioning

confidence: 99%

Section: Action System Refinementmentioning

confidence: 99%

Deriving real-time action systems with multiple time bands using algebraic reasoning

Dongol

Hayes

Derrick

2014

Science of Computer Programming

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“…Although these examples are easy these two problems clearly show the typical use of PAM. Because PAM is a reincarnation of POM within actors, it allows the implementation of advanced coordination mechanisms, like guards [22] and chords [18,21]. In this paper we show the PAM implementation of a coordination abstraction called Synchronizers [20].…”

Section: Canonical Examplesmentioning

confidence: 99%

Parallel actor monitors: Disentangling task-level parallelism from data partitioning in the actor model

Scholliers

Tanter

Meuter

2014

Science of Computer Programming

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While the actor model of concurrency is well appreciated for its ease of use, its scalability is often criticized. Indeed, the fact that execution within an actor is sequential prevents certain actor systems to take advantage of multicore architectures. In order to combine scalability and ease of use, we propose Parallel Actor Monitors (PAM), as a means to relax the sequentiality of intra-actor activity in a structured and controlled way. A PAM is a modular, reusable scheduler that permits to introduce intra-actor parallelism in a local and abstract manner. PAM allows the stepwise refinement of local parallelism within a system on a per-actor basis, without having to deal with low-level synchronization details and locks. We present the general model of PAM and its instantiation in the AmbientTalk language. Benchmarks confirm the expected performance gain.

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“…In order to achieve Q, regression is used to make sure that any action added to the existing plan will not interfere with P . Waldinger's regression is based on the idea of "weakest precondition" proposed by Dijkstra in 1975 [8](see also, e.g., [2,7]). Intuitively, regression from a logical sentence that is represented by a conjunction of goals, conj, via an action, A, yields another logical sentence that encodes what must be true before A is performed to make conj true immediately afterwards.…”

Section: Related Workmentioning

confidence: 99%

A State-Based Regression Formulation for Domains with Sensing Actions and Incomplete Information

Tuan¹,

Baral²,

Son³

2006

Logical Methods in Computer Science

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Abstract. We present a state-based regression function for planning domains where an agent does not have complete information and may have sensing actions. We consider binary domains and employ a three-valued characterization of domains with sensing actions to define the regression function. We prove the soundness and completeness of our regression formulation with respect to the definition of progression. More specifically, we show that (i) a plan obtained through regression for a planning problem is indeed a progression solution of that planning problem, and that (ii) for each plan found through progression, using regression one obtains that plan or an equivalent one.

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Guarded commands, nondeterminacy and formal derivation of programs

Cited by 1,511 publications

References 2 publications

Deriving real-time action systems with multiple time bands using algebraic reasoning

Deriving real-time action systems with multiple time bands using algebraic reasoning

Parallel actor monitors: Disentangling task-level parallelism from data partitioning in the actor model

A State-Based Regression Formulation for Domains with Sensing Actions and Incomplete Information

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