53 research outputs found
Symbolic Verification and Strategy Synthesis for Linearly-Priced Probabilistic Timed Automata
Probabilistic timed automata are a formalism for modelling systems whose dynamics includes probabilistic, nondeterministic and timed aspects including real-time systems. A variety of techniques have been proposed for the analysis of this formalism and successfully employed to analyse, for example, wireless communication protocols and computer security systems. Augmenting the model with prices (or, equivalently, costs or rewards) provides a means to verify more complex quantitative properties, such as the expected energy usage of a device or the expected number of messages sent during a protocol’s execution. However, the analysis of these properties on probabilistic timed automata currently relies on a technique based on integer discretisation of real-valued clocks, which can be expensive in some cases. In this paper, we propose symbolic techniques for verification and optimal strategy synthesis for priced probabilistic timed automata which avoid this discretisation. We build upon recent work for the special case of expected time properties, using value iteration over a zone-based abstraction of the model
An Individual-based Probabilistic Model for Fish Stock Simulation
We define an individual-based probabilistic model of a sole (Solea solea)
behaviour. The individual model is given in terms of an Extended Probabilistic
Discrete Timed Automaton (EPDTA), a new formalism that is introduced in the
paper and that is shown to be interpretable as a Markov decision process. A
given EPDTA model can be probabilistically model-checked by giving a suitable
translation into syntax accepted by existing model-checkers. In order to
simulate the dynamics of a given population of soles in different environmental
scenarios, an agent-based simulation environment is defined in which each agent
implements the behaviour of the given EPDTA model. By varying the probabilities
and the characteristic functions embedded in the EPDTA model it is possible to
represent different scenarios and to tune the model itself by comparing the
results of the simulations with real data about the sole stock in the North
Adriatic sea, available from the recent project SoleMon. The simulator is
presented and made available for its adaptation to other species.Comment: In Proceedings AMCA-POP 2010, arXiv:1008.314
Control Synthesis for Cyber-Physical Systems to Satisfy Metric Interval Temporal Logic Objectives under Timing and Actuator Attacks
This paper studies the synthesis of controllers for cyber-physical systems
(CPSs) that are required to carry out complex tasks that are time-sensitive, in
the presence of an adversary. The task is specified as a formula in metric
interval temporal logic (MITL). The adversary is assumed to have the ability to
tamper with the control input to the CPS and also manipulate timing information
perceived by the CPS. In order to model the interaction between the CPS and the
adversary, and also the effect of these two classes of attacks, we define an
entity called a durational stochastic game (DSG). DSGs probabilistically
capture transitions between states in the environment, and also the time taken
for these transitions. With the policy of the defender represented as a finite
state controller (FSC), we present a value-iteration based algorithm that
computes an FSC that maximizes the probability of satisfying the MITL
specification under the two classes of attacks. A numerical case-study on a
signalized traffic network is presented to illustrate our results
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