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33
Stochastic Process Algebra: From an Algebraic Formalism to an Architectural Description Language
 Performance Evaluation of Complex Systems: Techniques and Tools, LNCS
, 2002
"... Abstract. The objective of this tutorial is to describe the evolution of the field of stochastic process algebra in the past decade, through a presentation of the main achievements in the field. In particular, the tutorial stresses the current transformation of stochastic process algebra from a sim ..."
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Cited by 25 (14 self)
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Abstract. The objective of this tutorial is to describe the evolution of the field of stochastic process algebra in the past decade, through a presentation of the main achievements in the field. In particular, the tutorial stresses the current transformation of stochastic process algebra from a simple formalism to a fully fledged architectural description language for the functional verification and performance evaluation of complex computer, communication and software systems. 1
Stochastic transition systems for continuous state spaces and nondeterminism
 In FoSSaCS’05, LNCS 3441
, 2005
"... Abstract. We study the interaction between nondeterministic and probabilistic behaviour in systems with continuous state spaces, arbitrary probability distributions and uncountable branching. Models of such systems have been proposed previously. Here, we introduce a model that extends probabilistic ..."
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Cited by 18 (4 self)
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Abstract. We study the interaction between nondeterministic and probabilistic behaviour in systems with continuous state spaces, arbitrary probability distributions and uncountable branching. Models of such systems have been proposed previously. Here, we introduce a model that extends probabilistic automata to the continuous setting. We identify the class of schedulers that ensures measurability properties on executions, and show that such measurability properties are preserved by parallel composition. Finally, we demonstrate how these results allow us to define an alternative notion of weak bisimulation in our model. 1
Revisiting interactive Markov chains
 In Proc. Models for TimeCritical Systems
, 2002
"... 1 Introduction The advantages of using process algebras for the performance modeling and evaluation of concurrent systems due to their feature of compositionality have been widely recognized (see [12,2,18,9,5,3] and the references therein). Particularly simple and successful has been the extension o ..."
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Cited by 17 (1 self)
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1 Introduction The advantages of using process algebras for the performance modeling and evaluation of concurrent systems due to their feature of compositionality have been widely recognized (see [12,2,18,9,5,3] and the references therein). Particularly simple and successful has been the extension of standard process algebras with time delays whose duration follows an exponential probability distribution, called Markovian process algebras (see e.g. [12,2,18,9]). The &quot;timed &quot; behavior of systems specified with a Markovian process algebra can represented by a continuous time Markov chain (CTMC), i.e. a simple continuous time stochastic process where in each time point the future behavior of
Tutte le algebre insieme: Concepts, discussions and relations of stochastic process algebras with general distributions
 In Validation of Stochastic Systems
, 2004
"... Abstract. We report on the state of the art in the formal specification and analysis of concurrent systems whose activity duration depends on general probability distributions. First of all the basic notions and results introduced in the literature are explained and, on this basis, a conceptual clas ..."
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Cited by 17 (5 self)
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Abstract. We report on the state of the art in the formal specification and analysis of concurrent systems whose activity duration depends on general probability distributions. First of all the basic notions and results introduced in the literature are explained and, on this basis, a conceptual classification of the different approaches is presented. We observe that most of the approaches agree on the fact that the specification of systems with general distributions has a three level structure: the process algebra level, the level of symbolic semantics and the level of concrete semantics. Based on such observations, a new very expressive model is introduced for representing timed systems with general distributions. We show that many of the approaches in the literature can be mapped into this model establishing therefore a formal framework to compare these approaches. 1
Deciding and axiomatizing weak ST bisimulation for a process algebra with recursion and action refinement
 ACM Transactions on Computational Logic
, 2002
"... 1. INTRODUCTION ST semantics, originally defined in [van Glabbeek and Vaandrager 1987] over Petri Nets, is one of the most studied noninterleaving semantics. The main reason is that ST semantics is the less informative semantics that is a congruence for ..."
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Cited by 13 (6 self)
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1. INTRODUCTION ST semantics, originally defined in [van Glabbeek and Vaandrager 1987] over Petri Nets, is one of the most studied noninterleaving semantics. The main reason is that ST semantics is the less informative semantics that is a congruence for
A Uniform Framework for Modeling Nondeterministic, Probabilistic, Stochastic, or Mixed Processes and their Behavioral Equivalences
, 2013
"... Labeled transition systems are typically used as behavioral models of concurrent processes. Their labeled transitions define a onestep statetostate reachability relation. This model can be generalized by modifying the transition relation to associate a state reachability distribution with any pai ..."
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Cited by 8 (4 self)
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Labeled transition systems are typically used as behavioral models of concurrent processes. Their labeled transitions define a onestep statetostate reachability relation. This model can be generalized by modifying the transition relation to associate a state reachability distribution with any pair consisting of a source state and a transition label. The state reachability distribution is a function mapping each possible target state to a value that expresses the degree of onestep reachability of that state. Values are taken from a preordered set equipped with a minimum that denotes unreachability. By selecting suitable preordered sets, the resulting model, called ULTraS from Uniform Labeled Transition System, can be specialized to capture wellknown models of fully nondeterministic processes (LTS), fully probabilistic processes (ADTMC), fully stochastic processes (ACTMC), and nondeterministic and probabilistic (MDP) or nondeterministic and stochastic (CTMDP) processes. This uniform treatment of different behavioral models extends to behavioral equivalences. They can be defined on ULTraS by relying on appropriate measure functions that express the degree of reachability of a set of states when performing multistep computations. It is shown that the specializations of bisimulation, trace, and testing equivalences for the different classes of ULTraS coincide with the behavioral equivalences defined in the literature over traditional models except when nondeterminism and probability/stochasticity coexist; then new equivalences pop up.
Two Formal Approaches for Approximating Noninterference Properties
 FOUNDATIONS OF SECURITY ANALYSIS AND DESIGN II
, 2004
"... The formalisation of security properties for computer systems raises the problem of overcoming also in a formal setting the classical view according to which confidentiality is an absolute property stating the complete absence of any unauthorised disclosure of information. In this paper, we present ..."
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Cited by 7 (4 self)
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The formalisation of security properties for computer systems raises the problem of overcoming also in a formal setting the classical view according to which confidentiality is an absolute property stating the complete absence of any unauthorised disclosure of information. In this paper, we present two formal models in which the notion of noninterference, which is at the basis of a large variety of security properties defined in the recent literature, is approximated. To this aim, the definition of indistinguishability of process behaviour is replaced by a similarity notion, which introduces a quantitative measure ε of the behavioural difference among processes. The first model relies on a programming paradigm called Probabilistic Concurrent Constraint Programming, while the second one is presented in the setting of a probabilistic process algebra. In both models, appropriate notions of distance provide information (the ε) on the security level of the system at hand, in terms of the capability of an external observer of identifying illegal interferences.
Nondeterministic labeled Markov processes: Bisimulations and logical characterizations
 In Proc. of the 6th Int. Conf. on the Quantitative Evaluation of Systems (QEST 2009
, 2009
"... We extend the theory of labeled Markov processes with internal nondeterminism, a fundamental concept for the further development of a process theory with abstraction on nondeterministic continuous probabilistic systems. We define nondeterministic labeled Markov processes (NLMP) and provide both a s ..."
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Cited by 6 (3 self)
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We extend the theory of labeled Markov processes with internal nondeterminism, a fundamental concept for the further development of a process theory with abstraction on nondeterministic continuous probabilistic systems. We define nondeterministic labeled Markov processes (NLMP) and provide both a state based bisimulation and an event based bisimulation. We show the relation between them, including that the largest state bisimulation is also an event bisimulation. We also introduce a variation of the HennessyMilner logic that characterizes event bisimulation and that is sound w.r.t. the state base bisimulation for arbitrary NLMP. This logic, however, is infinitary as it contains a denumerable ∨. We then introduce a finitary sublogic that characterize both state and event bisimulation for image finite NLMP whose underlying measure space is also analytic. Hence, in this setting, all notions of bisimulation we deal with turn out to be equal. 1.
Performance Evaluation of Distributed Systems Based on a Discrete Real and StochasticTime Process Algebra
, 2009
"... We present a processalgebraic framework for performance evaluation of discretetime discreteevent systems. The modeling of the system builds on a process algebra with conditionallydistributed discretetime delays and generallydistributed stochastic delays. In the general case, the performance a ..."
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Cited by 2 (1 self)
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We present a processalgebraic framework for performance evaluation of discretetime discreteevent systems. The modeling of the system builds on a process algebra with conditionallydistributed discretetime delays and generallydistributed stochastic delays. In the general case, the performance analysis is done with the toolset of the modeling language χ by means of discreteevent simulation. The processalgebraic setting allows for expansion laws for the parallel composition and the maximal progress operator, so one can directly manipulate the process terms and transform the specification in a required form. This approach is illustrated by specifying and solving the recursive specification of the G/G/1/ ∞ queue, as well as by specifying a variant of the concurrent alternating bit protocol with generallydistributed unreliable channels. In a specific situation when all delays are assumed deterministic, we turn to performance analysis of probabilistic timed systems. This work employs discretetime probabilistic reward graphs, which comprise deterministic delays and immediate probabilistic choices. Here, we extend previous investigations on the topic, which only touched longrun analysis, to tackle transient analysis as well. The theoretical results obtained allow us to extend the χtoolset. For illustrative purposes, we analyze the concurrent alternating bit protocol in the extended environment of the χtoolset using discreteevent simulation for generallydistributed channels, the developed analytical method for deterministic channels, and Markovian analysis for exponentiallydistributed delays.