7,118 research outputs found
Parameterized Model-Checking for Timed-Systems with Conjunctive Guards (Extended Version)
In this work we extend the Emerson and Kahlon's cutoff theorems for process
skeletons with conjunctive guards to Parameterized Networks of Timed Automata,
i.e. systems obtained by an \emph{apriori} unknown number of Timed Automata
instantiated from a finite set of Timed Automata templates.
In this way we aim at giving a tool to universally verify software systems
where an unknown number of software components (i.e. processes) interact with
continuous time temporal constraints. It is often the case, indeed, that
distributed algorithms show an heterogeneous nature, combining dynamic aspects
with real-time aspects. In the paper we will also show how to model check a
protocol that uses special variables storing identifiers of the participating
processes (i.e. PIDs) in Timed Automata with conjunctive guards. This is
non-trivial, since solutions to the parameterized verification problem often
relies on the processes to be symmetric, i.e. indistinguishable. On the other
side, many popular distributed algorithms make use of PIDs and thus cannot
directly apply those solutions
Modeling a distributed Heterogeneous Communication System using Parametric Timed Automata
In this report, we study the application of the Parametric Timed Automata(PTA) tool to a concrete case of a distributed Heterogeneous Communication System (HCS). The description and requirements of HCS are presented and the system modeling is explained carefully. The system models are developed in UPPAAL and validated by different test cases. Part of the system models are then converted into parametric timed automata and the schedulability checking is run to produce the schedulability regions
PRM113 - Timed Automata Modeling of The Personalized Treatment Decisions In Metastatic Castration Resistant Prostate Cancer
Objectives\ud
The Timed Automata modeling paradigm has emerged from Computer Science as a mature tool for the functional analysis and performance evaluation of timed distributed systems. This study is a first exploration of the suitability of Timed Automata for health economic modeling, using a case study on personalized treatment for metastatic Castration Resistant Prostate Cancer (mCRPC).\ud
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Methods\ud
The treatment process has been modeled by creating several independent timed automata, where an automaton represents a patient, a physician, a test, or a treatment/testing guideline schedule. These automata interact via message passing and are fully parameterized with quantitative information. Messages can be passed, asynchronously, from one automaton to one or more other automata, at any point in time, thereby triggering events and decisions in the treatment process. In the automata time is continuous, and both QALYs and costs can be incorporated using (assignable) local clocks. Uncertainty can be modeled using probabilities and timing intervals that can be uniformly or exponentially distributed. Software for building timed automata is freely available for academic use and includes procedures for statistical model checking (SMC) to validate the (internal) behavior and results of the model.\ud
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Results\ud
In several days a Timed Automata model has been produced that is compositional, easy to understand and easy to update. The behavior and results of the model have been assessed using the SMC tool. Actual results for the mCRPC case study obtained from the Timed Automata model are compared with results of a Discrete Event Simulation model in a separate study.\ud
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Conclusions\ud
The Timed Automata paradigm can be successfully applied to evaluate the potential benefits of a personalized treatment process of mCRPC. The compositional nature of the resulting model provides a good separation of all relevant components. This leads to models that are easy to formulate, validate, understand, maintain and update
Expected-Delay-Summing Weak Bisimilarity for Markov Automata
A new weak bisimulation semantics is defined for Markov automata that, in
addition to abstracting from internal actions, sums up the expected values of
consecutive exponentially distributed delays possibly intertwined with internal
actions. The resulting equivalence is shown to be a congruence with respect to
parallel composition for Markov automata. Moreover, it turns out to be
comparable with weak bisimilarity for timed labeled transition systems, thus
constituting a step towards reconciling the semantics for stochastic time and
deterministic time.Comment: In Proceedings QAPL 2015, arXiv:1509.0816
On Zone-Based Analysis of Duration Probabilistic Automata
We propose an extension of the zone-based algorithmics for analyzing timed
automata to handle systems where timing uncertainty is considered as
probabilistic rather than set-theoretic. We study duration probabilistic
automata (DPA), expressing multiple parallel processes admitting memoryfull
continuously-distributed durations. For this model we develop an extension of
the zone-based forward reachability algorithm whose successor operator is a
density transformer, thus providing a solution to verification and performance
evaluation problems concerning acyclic DPA (or the bounded-horizon behavior of
cyclic DPA).Comment: In Proceedings INFINITY 2010, arXiv:1010.611
Handshaking Protocol for Distributed Implementation of Reo
Reo, an exogenous channel-based coordination language, is a model for service
coordination wherein services communicate through connectors formed by joining
binary communication channels. In order to establish transactional
communication among services as prescribed by connector semantics, distributed
ports exchange handshaking messages signalling which parties are ready to
provide or consume data. In this paper, we present a formal implementation
model for distributed Reo with communication delays and outline ideas for its
proof of correctness. To reason about Reo implementation formally, we introduce
Timed Action Constraint Automata (TACA) and explain how to compare TACA with
existing automata-based semantics for Reo. We use TACA to describe handshaking
behavior of Reo modeling primitives and argue that in any distributed circuit
remote Reo nodes and channels exposing such behavior commit to perform
transitions envisaged by the network semantics.Comment: In Proceedings FOCLASA 2014, arXiv:1502.0315
Parametric Schedulability Analysis of Fixed Priority Real-Time Distributed Systems
Parametric analysis is a powerful tool for designing modern embedded systems,
because it permits to explore the space of design parameters, and to check the
robustness of the system with respect to variations of some uncontrollable
variable. In this paper, we address the problem of parametric schedulability
analysis of distributed real-time systems scheduled by fixed priority. In
particular, we propose two different approaches to parametric analysis: the
first one is a novel technique based on classical schedulability analysis,
whereas the second approach is based on model checking of Parametric Timed
Automata (PTA).
The proposed analytic method extends existing sensitivity analysis for single
processors to the case of a distributed system, supporting preemptive and
non-preemptive scheduling, jitters and unconstrained deadlines. Parametric
Timed Automata are used to model all possible behaviours of a distributed
system, and therefore it is a necessary and sufficient analysis. Both
techniques have been implemented in two software tools, and they have been
compared with classical holistic analysis on two meaningful test cases. The
results show that the analytic method provides results similar to classical
holistic analysis in a very efficient way, whereas the PTA approach is slower
but covers the entire space of solutions.Comment: Submitted to ECRTS 2013 (http://ecrts.eit.uni-kl.de/ecrts13
Modelamiento y especificación de sistemas distribuidos y temporizados
El aumento en la complejidad de los sistemas distribuidos y temporizados hace que ellos sean muy difícil de modelary especificar correctamente. Diferentes métodos formales son útiles para el proceso de modelado y especificaciónde estos tipos de sistemas. Los Autómatas Temporizados (AT) y los Autómatas Temporizados Distribuidos (ATD)son los modelos formales más utilizados para modelar sistemas de tiempo real y distribuidos. Lamentablemente losalgoritmos existentes para calcular la inclusión y complementación de sus lenguajes son indecidible. En este artículo,presentaremos las lógicas (Lógica Temporalizada de Eventos Distribuidos, Lógica Temporizados de Memorizaciónde Eventos) y los autómatas (Autómatas de Eventos Distribuidos, Autómatas de Memorización de Eventos),totalmente decidibles. Estos métodos fueron diseñados para modelar, especificar, estudiar el comportamiento y enespecial verificar el buen funcionamiento de los sistemas de tiempo real y distribuidos.Increasing complexity in distributed and real-time systems makes them very hard to model and specify correctly.
Different formal methods are useful for the process of modeling and specification of these kinds of systems.
Timed Automata (TA) and Distributed Timed Automata (DTA) are the dominant models of distributed and realtime
systems. Unfortunately, their language inclusion and complementation are undecidable. In this paper, we
will present logics and automata (Distributed Event Clock Automata (DECA), Memory Event Clock Automata
(RMECA), Distributed Event Clock Temporal Logic (DECTL), Memory Event Clock Temporal Logic (RMECTL)
fully decidable and they were designed to modeling, specifying and studying the behavior and in particular verifying
the correct operation of distributed and real-time systems
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