239 research outputs found
Web Application for Visual Modeling of Discrete Event Systems
This research work has resulted in the development of a web application that enables discrete event systems simulation to be created using a Petri-object approach. It provides the development of a model in two stages. In the first stage, the dynamics of the classes of objects are created using Petri net. In the second stage, the model is composed of objects with given dynamics. The simulation algorithm is based on stochastic Petri net with multichannel transitions and is implemented using Ruby. The web application enables the design of the model's dynamics by manipulation with graphics objects and saving it not only as a graphics object but also as a program method. This greatly improves the overall performance of the simulation model development
Formal VeriïŹcation of AADL models with Fiacre and Tina
9 pagesInternational audienceThis paper details works undertaken in the scope of the Spices project concerning the behavioral verification of AADL models. We give a high-level view of the tools involved and describe the successive transformations performed by our verification process. We also report on an experiment carried out in order to evaluate our framework and give the first experimental results obtained on real-size models. This demonstrator models a network protocol in charge of data communications between an airplane and ground stations. From this study we draw a set of conclusions about the integration of model-checking tools in an industrial development process
Petri net based development of globally-asynchronous locally-synchronous distributed embedded systems
Dissertação para obtenção do Grau de Doutor em Engenharia Electrotécnica e de ComputadoresA model-based development approach (MBDA) for Globally-Asynchronous Locally-
Synchronous (GALS) Distributed Embedded Systems (DESs) is proposed. This approach
relies on the GALS-DESs specification through (low- or high-level) Petri net classes, which
ensure that the created models are GALS, locally deterministic, distributable, networkindependent,
and platform-independent and support their simulation, verification, and
implementation (using simulation, model-checking, and code generation tools). The use
of network- and platform-independent models enable the use of heterogeneous communication
networks to support the distributed components interaction and enable the use
of heterogeneous platforms to support the components and the communication nodes
implementation. To enable the proposed MBDA, Petri nets are extended with a set of the
concepts, most notably time-domains and asynchronous-channels. Algorithms to support
the verification of GALS-DES models and their decomposition into implementable
sub-models are also proposed. A tool chain framework (IOPT-tools) was extended with
this work proposals, supporting their validation and the GALS-DESs development.Fundação para a CiĂȘncia e a Tecnologia - grant ref. SFRH/BD/62171/200
Decision systems : the relation between problem specification and mathematical analysis
In this paper it is demonstrated that automated support for decision making of a tactical or strategic nature requires a solver-independent medium for describing decision situations. Such a medium may be specific for one environment, but it is also possible to develop media for certain types of environments. By using such a medium one obtains a decoupling of problem formulation and method of analysis. This makes it possible to use (parts of) the problem formulation as input for different types of models. Such problem formulations may provide mathematical models themselves, although they might also contain some less formal features. The decoupling makes it possible to choose problem formulations which are much closer to the original decision situation than would otherwise be possible with formulations in terms of a preselected solver. The argumentation is illustrated by treating a language for specifying goods flow problems in some detail. This language is based on timed coloured Petri-nets
Preemptive D-timed Petri nets, timeouts, modeling and analysis of communication protocols
Preemptive D-timed Petri nets are Petri nets with deterministic firing times and with generalized inhibitor arcs to interrupt firing transitions. A formalism is presented which represents the behavior of free-choice D-timed Petri nets by discrete-space discrete-time semi-Markov processes. Stationary probabilities of states can thus be determined by standard techniques used for analysis of Markov chains. A straightforward application of timed Petri nets is modelling and analysis of systems of asynchronous communicating processes, and in particular communication protocols. Places of Petri nets model queues of messages, transitions represent delays in communication networks, interrupt arcs conveniently model timeout mechanisms, and probabilities associated with free-choice classes correspond to relative frequencies of random events. Simple protocols are used as an illustration of modelling and analysis
Performance evaluation using extended timed Petri nets
It is shown that the behavior of extended limited-choice Petri nets with exponentially distributed firing times can be represented by probabilistic state graphs. For bounded Petri nets, the corresponding state graphs are finite, stationary descriptions can thus be obtained by standard techniques used for analysis of continuous-time finite-state homogenous Markov chains. An immediate application of such a model is performance analysis of concurrent systems, and in particular queueing systems with exponentially distributed interarrival and service times. A simple model of an interactive computer system with priority scheduling is used as an illustration of performance evaluation, and a short comparison of timed Petri nets with stochastic Petri nets is given
Independent verification of specification models for large software systems at the early phases of development lifecycle
One of the major challenges facing the software industry, in general and IV&V (Independent Verification and Validation) analysts in particular, is to find ways for analyzing dynamic behavior of requirement specifications of large software systems early in the development lifecycle. Such analysis can significantly improve the performance and reliability of the developed systems. This dissertation addresses the problem of developing an IV&V framework for extracting semantics of dynamic behavior from requirement specifications based on: (1) SART (Structured Analysis with Realtime) models, and (2) UML (Unified Modeling Language) models.;For SART, the framework presented here shows a direct mapping from SART specification models to CPN (Colored Petrinets) models. The semantics of the SART hierarchy at the individual levels are preserved in the mapping. This makes it easy for the analyst to perform the analysis and trace back to the corresponding SART model. CPN was selected because it supports rigorous dynamic analysis. A large scale case study based on a component of NASA EOS system was performed for a proof of the concept.;For UML specifications, an approach based on metamodels is presented. A special type of metamodel, called dynamic metamodel (DMM), is introduced. This approach holds several advantages over the direct mapping of UML to CPN. The mapping rules for generating DMM are not CPN specific, hence they would not change if a language other than CPN is used. Also it makes it more flexible to develop DMM because other types of models can be added to the existing UML models. A simple example of a pacemaker is used to illustrate the concepts of DMM
Reliable Industrial IoT-Based Distributed Automation
Reconfigurable manufacturing systems supported by Industrial Internet-of-Things (IIoT) are modular and easily integrable, promoting efficient system/component reconfigurations with minimal downtime. Industrial systems are commonly based on sequential controllers described with Control Interpreted Petri Nets (CIPNs). Existing design methodologies to distribute centralized automation/control tasks focus on maintaining functional properties of the system during the process, while disregarding failures that may occur during execution (e. g., communication packet drops, sensing or actuation failures). Consequently, in this work, we provide a missing link for reliable IIoT-based distributed automation. We introduce a method to transform distributed control models based on CIPNs into Stochastic Reward Nets that enable integration of realistic fault models (e. g., probabilistic link models). We show how to specify desired system properties to enable verification under the adopted communication/fault models, both at design-and run-time; we also show feasibility of runtime verification on the edge, with a continuously updated system model. Our approach is used on real industrial systems, resulting in modifications of local controllers to guarantee reliable system operation in realistic IIoT environments
Modified D-timed Petri nets, timeouts, and modelling of communication protocols
Modified D-timed Petri nets are Petri nets with âspe-
cialâ arcs to interrupt firing transitions, and with deter-
ministic firing times; these special arcs are called âin-
terruptâ arcs. It is shown that the behaviour of simple
modified bounded free-choice D-timed Petri nets can be
represented by finite probabilistic state graphs, stationary
probabilities of states can thus be obtained by standard
techniques used for analysis of Markov chains. An imme-
diate application of such a model is performance analysis
of systems of interacting asynchronous processes, and in
particular communication protocols. Places of Petri nets
model queues of messages, transitions represent events
in communication networks, interrupt arcs conveniently
model timeouts, and probabilities associated with free-
choice classes correspond to relative frequencies of random events. A simple protocol based on unnumbered messages and acknowledgements is used as an illustration of analy-
sis
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