Sound reasoning in tock-CSP

Baxter, Jim; Ribeiro, Pedro; Cavalcanti, Ana

doi:10.1007/s00236-020-00394-3

Cited by 20 publications

(20 citation statements)

References 37 publications

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“…This will require us to consider discrete time, which we believe can be supported using a dedicated time event in ITrees, similar to tock-CSP [31]. This will build on our colleagues' work with ✓-tock [1], a new semantics for tock-CSP. This will open up a pathway from graphical models to verified implementations of autonomous robotic controllers.…”

Section: Discussionmentioning

confidence: 99%

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Formally Verified Simulations of State-Rich Processes using Interaction Trees in Isabelle/HOL

Foster¹,

Hur²,

Woodcock³

2021

Preprint

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Simulation and formal verification are important complementary techniques necessary in high assurance model-based systems development. In order to support coherent results, it is necessary to provide unifying semantics and automation for both activities. In this paper we apply Interaction Trees in Isabelle/HOL to produce a verification and simulation framework for state-rich process languages. We develop the core theory and verification techniques for Interaction Trees, use them to give a semantics to the CSP and Circus languages, and formally link our new semantics with the failures-divergences semantic model. We also show how the Isabelle code generator can be used to generate verified executable simulations for reactive and concurrent programs.

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Section: Discussionmentioning

confidence: 99%

“…Isabelle's code generator allows us to automatically produce ITreebased simulations, which allows a tight development loop, where simulation and verification activities are intertwined. All our results have been mechanised, and can be found in the accompanying repository 1 , and specific icon links ( / ) next to each result.…”

Section: Introductionmentioning

confidence: 99%

Formally Verified Simulations of State-Rich Processes using Interaction Trees in Isabelle/HOL

Foster¹,

Hur²,

Woodcock³

2021

Preprint

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“…The healthiness conditions of -tock [13], whose composition is named TT, ensure properties of the standard models of CSP in the context of TT traces. Namely, the empty trace is an observation of every process; prefix closure and subset closure of refusals; and an event that cannot be performed is refused.…”

Section: Definition 1 Obsmentioning

confidence: 99%

“…Thus, FDR actually implements a constrained form of Pri ≤ , where, for example, and τ are maximal in the order. However, this is insufficient for Pri ≤ to be congruent over weaker models such as -tock [13] and the stable-failures (F [1]). Process S makes an internal choice (⊓) between offering events a, or b, and terminating, or waiting a time unit (Wait 1) and then behaving as S again, specified using sequential composition ( ; ).…”

Section: Introductionmentioning

confidence: 99%

“…In this paper we calculate a definition of Pri ≤ for tock -CSP via a stepwise Galois connection between the F L model and the -tock model [13], the only sound model for tock -CSP that can be used to reason about timed refinement, and that captures deadlines, termination and erroneous Zeno behaviour. It is a faithful account of the tock -CSP dialect and is mechanised in Isabelle/HOL [14].…”

Section: Introductionmentioning

confidence: 99%

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Priorities in tock-CSP

Ribeiro,

Baxter,

Cavalcanti

2019

Preprint

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The tock -CSP encoding embeds a rich and flexible approach to modelling discrete timed behaviours in CSP where the event tock is interpreted to mark the passage of time. The model checker FDR provides tailored support for tock -CSP, including a prioritisation operator that has typically been used to ensure maximal progress, where time only advances after internal activity has stabilised. Prioritisation may also be used on its own right as a modelling construct. Its operational semantics, however, is only congruent over the most discriminating semantic model of CSP: the finite-linear model. To enable sound and compositional reasoning in a tock -CSP setting, we calculate a denotational definition for prioritisation. For that we establish a Galois connection between a specialisation of the finite-linear model, with tock and , that signals termination, as special events, and -tock -CSP, a model for tock -CSP that captures termination, deadlines, and is adequate for reasoning about timed refinement. Our results are mechanised using Isabelle/HOL.

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RoboCert: Property Specification in Robotics

Windsor

Cavalcanti

2022

Formal Methods and Software Engineering

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RoboStar is a toolkit for model-based development using a domain-specific notation, RoboChart, with enriched UML-like state machines and a custom component model. We present RoboCert: a novel notation, based on UML sequence diagrams, which facilitates the specification of properties over RoboChart components. With RoboCert, we can express properties of a robotic system in a user-friendly, idiomatic manner. RoboCert specifications can be existential or universal, include timing notions such as deadlines and budgets, and both safety and liveness properties. Our work is faithful to UML where it can be, but presents significant extensions to fit the robotics application needs. RoboCert comes with tooling support for modelling and verification by model checking, and formal semantics in tock -CSP, the discrete-time variant of CSP.

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Sound reasoning in tock-CSP

Cited by 20 publications

References 37 publications

Formally Verified Simulations of State-Rich Processes using Interaction Trees in Isabelle/HOL

Formally Verified Simulations of State-Rich Processes using Interaction Trees in Isabelle/HOL

Priorities in tock-CSP

RoboCert: Property Specification in Robotics

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