H. Hansson. Time and Probabilities in Formal Design of Distributed Systems. Elsevier, 1994.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....property. We expect some interesting foundational questions to arise in the formulation of security properties such as authentication and secrecy. It may also be possible to develop model checking procedures along the lines of these already explored for probabilistic temporal logics [HJ89, Han94, dA97, HK97] In fact, we hope to be able to develop automated reasoning procedures for use in a network security setting using techniques developed in our study of the properties of our process calculus. Acknowledgements: Thanks to M. Abadi, R. Amadio, D. Boneh, R. Canetti, C. Dwork, R. van ....

H. Hansson. Time and Probabilities in Formal Design of Distributed Systems. Real-Time Safety Critical Systems. Elsevier, 1994.

....transition is an element in S Theta Dist(Act Theta S) i.e. the probability distribution also includes a distribution over the possible actions. If all actions in a distribution are identical, we get the above definition of a probabilistic transition system 1 . Several researchers (e.g. [30, 17] have noticed that it is not trivial to define a symmetric parallel composition operator in the generative model. One source of difficulty is that in a generative model, a probabilistic transition system defines in each of its states a probability distribution 1 Note that the above notion of ....

....15 0:6 , which expresses that the property will hold within 15 transition steps with probability at least 0:6. The presented model checking algorithms rely on results on Markov chains and dynamic programming. Later, the logic PCTL was extended to systems including non determinism by Hansson in [30] and Segala and Lynch in [52] Christoff and Christoff [12] adapt a restricted form of the modal mu calculus. A new probabilistic semantics for the mu calculus has been developed by Narasimha et al. 45] Aziz et al. [2] introduces pCTL a probabilistic extension of CTL . Here the model checking ....

H. Hansson. Time and Probabilities in Formal Design of Distributed Systems. Real-Time Safety Critical Systems. Elsevier, 1994.

....of the system; once the policy is fixed, the MDP is reduced to a conventional stochastic process. A simple way to introduce time in these models is to associate with each pair consisting of state and of a related action the time (or the expected time) spent at the state when the action is selected [Han94, Seg95, dA98]. One of the basic questions we can ask about the timing behavior of such a system is the expected time needed to reach a given set of target states from a specified starting state. Being able to answer this question opens the way to the automated verification of systems properties such as ....

....target can be disregarded in the solution of the optimization problem, and the SSP problem can be solved by determining the policy that minimizes the total cost. If the starting and target states are part of a formal specification, or if the time associated with state action pairs can be 0, as in [Han94, Seg95, dA97, dA98], these assumptions do not hold in general, and new solution methods are required. The aim of this paper is to present methods for solving the SSP problem that rely on the assumptions that the costs are all non negative, or all non positive. We call the SSP problems that satisfy these assumptions ....

H. Hansson. Time and Probabilities in Formal Design of Distributed Systems. Real-Time Safety Critical Systems Series. Elsevier, 1994.

....The logics pCTL and pCTL are derived from the branching time logics CTL and CTL [6] by introducing a probabilistic operator IP, with the intuitive reading that IP a OE (resp. IP a OE) means that the probability of OE holding in the future evolution of the system is at least (resp. at most) a [10, 11, 9, 2]. Formally, we distinguish two classes of formulas: the class Stat of state formulas (whose truth value is evaluated on the states) and the class Seq of sequence formulas (whose truth value is evaluated on infinite sequences of states) For pCTL , the classes Stat and Seq are defined as follows: ....

H. Hansson. Time and Probabilities in Formal Design of Distributed Systems. Real-Time Safety Critical Systems. Elsevier, 1994.

....The logics pCTL and pCTL are derived from the branching time logics CTL and CTL [6] by introducing a probabilistic operator IP, with the intuitive reading that IP a OE (resp. IP a OE) means that the probability of OE holding in the future evolution of the system is at least (resp. at most) a [10, 11, 9, 2]. Formally, we distinguish two classes of formulas: the class Stat of state formulas (whose truth value is evaluated on the states) and the class Seq of sequence formulas (whose truth value is evaluated on infinite sequences of states) For pCTL , the classes Stat and Seq are defined as follows: ....

H. Hansson. Time and Probabilities in Formal Design of Distributed Systems. Real-Time Safety Critical Systems. Elsevier, 1994.

....familiar with the mathematical formalisms for describing concurrent processes that are collectively referred to as process algebras. For an introduction to the theory and application of process algebras the texts [Mil89, BW90] are recommended. In this paper we build on the work by Hansson [Han91, Han94] in which constructs for describing discretely timed and probabilistic processes are added to the CCS process algebra. The resulting algebra is named TPCCS, short for Timed Probabilistic Calculus of Communicating Systems. The probabilistic extension to CCS is made by introducing a binary ....

....then time cannot pass; the internal action will happen at once, i.e, before the occurrence of the next time quantum. The arbitrary waiting rule in contrast allows a process to wait infinitely long before synchronising with its environment, as long as no internal actions are possible. Hansson [Han94] provides a definition of what it means for two TPCCS processes to have the same behaviour by adopting the strong bisimulation equivalence to TPCCS. Additionally, Hansson defines a logic, Timed Probabilistic concurrent Computation Tree Logic (abbreviated TPCTL) that can be used to express and ....

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H. Hansson. Time and Probabilities in Formal Design of Distributed Systems. Real-Time Safety Critical Systems. Elsevier, 1994. Forthcoming.

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H. Hansson. Time and Probabilities in Formal Design of Distributed Systems. Elsevier, 1994.

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Hansson, H. Time and Probabilities in Formal Design of Distributed Systems. Real-Time Safety Critical Systems. Elsevier, 1994.

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H. Hansson. Time and Probabilities in Formal Design of Distributed Systems. Real-Time Safety Critical Systems Series. Elsevier, 1994.

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Hansson, H. Time and Probabilities in Formal Design of Distributed Systems. Real-Time Safety Critical Systems. Elsevier, 1994.

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H. Hansson. Time and Probabilities in Formal Design of Distributed Systems. Elsevier, 1994.

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H. Hansson. Time and Probabilities in Formal Design of Distributed Systems. Real-Time Safety Critical Systems Series. Elsevier, 1994.

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