Modeling Timed Concurrent Systems

Liu, Xiaojun; Matsikoudis, Eleftherios; Lee, Edward A.

doi:10.1007/11817949_1

Cited by 32 publications

(39 citation statements)

References 21 publications

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“…It has played a crucial role in allowing us to explore the language design space and to converge on an expressive, minimal syntax for modeling hybrid systems and on a formal (exact) semantics for solutions. Among other design choices, it allowed us to make an early decision to support the notion of super-dense time, first introduced in the verification literature [12], and later advocated by Liu, Matsikoudis and Lee [11]. This notion facilitates modeling of discrete subsystems with multiple idealized (zero time) and externally-observable internal transitions.…”

Section: A Syntax and Informal Semanticsmentioning

confidence: 99%

Accurate rigorous simulation should be possible for good designs

Duracz

Bartha

Taha

2016

2016 International Workshop on Symbolic and Numerical Methods for Reachability Analysis (SNR)

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The development of Cyber-Physical Systems benefits from better methods and tools to support the simulation and verification of hybrid (continuous/discrete) models. Acumen is an open source testbed for exploring the design space of what rigorous-butpractical next-generation tools can deliver to developers. Central to Acumen is the notion of rigorous simulation. Like verification tools, rigorous simulation is intended to provide guarantees about the behavior of the system. Like traditional simulation tools, it is intended to be intuitive, practical, and scalable. Whether these two goals can be achieved simultaneously is an important, longterm challenge.This paper proposes a design principle that can play an important role in meeting this challenge. The principle addresses the criticism that accumulating numerical errors is a serious impediment to practical rigorous simulation. It is inspired by a twofold insight: one relating to the nature of systems engineered in the real world, and the other relating to how numerical errors in the simulation of a model can be recast as errors in the state or parameters of the model in the simulation. We present a suite of small, concrete benchmarks that can be used to assess the extent to which a rigorous simulator upholds the proposed principle. We also report on which benchmarks Acumen's current rigorous simulator already succeeds and which ones remain challenging.

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Section: A Syntax and Informal Semanticsmentioning

confidence: 99%

Accurate rigorous simulation should be possible for good designs

Duracz

Bartha

Taha

2016

2016 International Workshop on Symbolic and Numerical Methods for Reachability Analysis (SNR)

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“…Non-causal I/O relationships are problematic. Semantics of discrete-event, continuous-time, and hybrid systems models all rely on causal I/O relationships [22,8,11,12,14].…”

Section: Zero-crossing Detectormentioning

confidence: 99%

Requirements for Hybrid Cosimulation

Broman¹,

Greenberg²,

Lee³

et al. 2014

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Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. Abstract This paper defines a suite of requirements for future hybrid cosimulation standards, and specifically provides guidance for development of a hybrid cosimulation version of the Functional Mockup Interface (FMI) standard. A cosimulation standard defines interfaces that enable diverse simulation tools to interoperate. Specifically, one tool defines a component that forms part of a simulation model in another tool. We focus on components with inputs and outputs that are functions of time, and specifically on inputs and outputs that are mixtures of discrete events and continuous time signals. This hybrid mixture is not well supported by existing cosimulation standards, and specifically not by FMI 2.0, for reasons that are explained in this paper. The paper defines a suite of test components, giving a mathematical model of an ideal behavior, plus a discussion of practical implementation considerations. The discussion includes acceptance criteria by which we can determine whether a standard supports definition of each component. In addition, the paper defines a set of test compositions of components. These compositions define requirements for coordination between components, including consistent handling of timed events.

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“…At the same time, it may well be that the relevant fixed-point theorem of Priess-Crampe and Ribenboim is independent of the theory of generalized ultrametric spaces in the classical Zermelo-Fraenkel set theory without choice, thus lacking a constructive proof altogether. 33 The answer lies in the non-constructive proof of Theorem 5.2. Indeed, the proof contains all the ingredients of a transfinite recursion facilitating the construction of a chain that may effectively substitute for the maximal one only asserted to exist therein by an appeal to Kuratowski's Lemma.…”

Section: Constructionmentioning

confidence: 99%

On Fixed Points of Strictly Causal Functions

Matsikoudis

Lee

2013

Lecture Notes in Computer Science

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We ask whether strictly causal components form well defined systems when arranged in feedback configurations. The standard interpretation for such configurations induces a fixed-point constraint on the function modelling the component involved. We define strictly causal functions formally, and show that the corresponding fixed-point problem does not always have a well defined solution. We examine the relationship between these functions and the functions that are strictly contracting with respect to a generalized distance function on tagged signals, and argue that these strictly contracting functions are actually the functions that one ought to be interested in. We prove a constructive fixed-point theorem for these functions, introduce a corresponding induction principle, and study the related convergence process.

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Modeling Timed Concurrent Systems

Cited by 32 publications

References 21 publications

Accurate rigorous simulation should be possible for good designs

Accurate rigorous simulation should be possible for good designs

Requirements for Hybrid Cosimulation

On Fixed Points of Strictly Causal Functions

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