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On the Semantics of Markov Automata
"... Abstract. Markov automata describe systems in terms of events which may be nondeterministic, may occur probabilistically, or may be subject to time delays. We define a novel notion of weak bisimulation for such systems and prove that this provides both a sound and complete proof methodology for a na ..."
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Abstract. Markov automata describe systems in terms of events which may be nondeterministic, may occur probabilistically, or may be subject to time delays. We define a novel notion of weak bisimulation for such systems and prove that this provides both a sound and complete proof methodology for a natural extensional behavioural equivalence between such systems, a generalisation of reduction barbed congruence, the wellknown touchstone equivalence for a large variety of process description languages. 1
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 9 (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.
Weak Markovian Bisimulation Congruences and Exact CTMCLevel Aggregations for
 Sequential Processes”, in Proc. of TGC 2011, LNCS 7173:89–103
"... We have recently defined a weak Markovian bisimulation equivalence in an integratedtime setting, which reduces sequences of exponentially timed internal actions to individual exponentially timed internal actions having the same average duration and execution probability as the corresponding sequenc ..."
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Cited by 7 (2 self)
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We have recently defined a weak Markovian bisimulation equivalence in an integratedtime setting, which reduces sequences of exponentially timed internal actions to individual exponentially timed internal actions having the same average duration and execution probability as the corresponding sequences. This weak Markovian bisimulation equivalence is a congruence for sequential processes with abstraction and turns out to induce an exact CTMClevel aggregation at steady state for all the considered processes. However, it is not a congruence with respect to parallel composition. In this paper, we show how to generalize the equivalence in a way that a reasonable tradeoff among abstraction, compositionality, and exactness is achieved for concurrent processes. We will see that, by enhancing the abstraction capability in the presence of concurrent computations, it is possible to retrieve the congruence property with respect to parallel composition, with the resulting CTMClevel aggregation being exact at steady state only for a certain subset of the considered processes. 1
Uniform Labeled Transition Systems for Nondeterministic, Probabilistic, and Stochastic Processes. In:
 Proc. of the 5th Int. Symp. on Trustworthy Global Computing (TGC 2010), LNCS 6084, Springer,
, 2010
"... Labeled transition systems are typically used to represent the behavior of nondeterministic processes, with labeled transitions defining a onestep statetostate reachability relation. This model has been recently made more general by modifying the transition relation in such a way that it associa ..."
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Cited by 5 (1 self)
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Labeled transition systems are typically used to represent the behavior of nondeterministic processes, with labeled transitions defining a onestep statetostate reachability relation. This model has been recently made more general by modifying the transition relation in such a way that it associates with any source state and transition label a reachability distribution, i.e., a function mapping each possible target state to a value of some domain that expresses the degree of onestep reachability of that target state. In this extended abstract, we show how the resulting model, called ULTRAS from Uniform Labeled TRAnsition System, can be naturally used to give semantics to a fully nondeterministic, a fully probabilistic, and a fully stochastic variant of a CSPlike process language.
On a Uniform Framework for the Definition of Stochastic Process Languages
, 2009
"... In this paper we show how Rate Transition Systems (RT Ss) can be used as a unifying framework for the definition of the semantics of stochastic process algebras. RT Ss facilitate the compositional definition of such semantics exploiting operators on the next state functions which are the functiona ..."
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Cited by 3 (1 self)
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In this paper we show how Rate Transition Systems (RT Ss) can be used as a unifying framework for the definition of the semantics of stochastic process algebras. RT Ss facilitate the compositional definition of such semantics exploiting operators on the next state functions which are the functional counterpart of classical process algebra operators. We apply this framework to representative fragments of major stochastic process calculi namely TIPP, PEPA and IML and show how they solve the issue of transition multiplicity in a simple and elegant way. We, moreover, show how RT Ss help describing different languages, their differences and their similarities. For each calculus, we also show the formal correspondence between the RT Ss semantics and the standard SOS one.
Exploiting the hierarchical structure of rulebased
"... specifications for decision planning ..."
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On the Expressiveness of Markovian Process Calculi with Durational and Durationless Actions
"... Several Markovian process calculi have been proposed in the literature, which differ from each other for various aspects. With regard to the action representation, we distinguish between integratedtime Markovian process calculi, in which every action has an exponentially distributed duration associ ..."
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Cited by 2 (2 self)
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Several Markovian process calculi have been proposed in the literature, which differ from each other for various aspects. With regard to the action representation, we distinguish between integratedtime Markovian process calculi, in which every action has an exponentially distributed duration associated with it, and orthogonaltime Markovian process calculi, in which action execution is separated from time passing. Similar to deterministically timed process calculi, we show that these two options are not irreconcilable by exhibiting three mappings from an integratedtime Markovian process calculus to an orthogonaltime Markovian process calculus that preserve the behavioral equivalence of process terms under different interpretations of action execution: eagerness, laziness, and maximal progress. The mappings are limited to classes of process terms of the integratedtime Markovian process calculus with restrictions on parallel composition and do not involve the full capability of the orthogonaltime Markovian process calculus of expressing nondeterministic choices, thus elucidating the only two important differences between the two calculi: their synchronization disciplines and their ways of solving choices. 1
Performability Measure Specification: Combining CSRL and MSL
"... An integral part of the performance modeling process is the specification of the performability measures of interest. The notations proposed for this purpose can be grouped into classes that differ from each other in their expressiveness and usability. Two representative notations are the continuo ..."
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An integral part of the performance modeling process is the specification of the performability measures of interest. The notations proposed for this purpose can be grouped into classes that differ from each other in their expressiveness and usability. Two representative notations are the continuous stochastic reward logic CSRL and the measure specification language MSL. The former is a stochastic temporal logic formulating quantitative properties about states and paths, while the latter is a componentoriented specification language relying on a firstorder logic for defining rewardbased measures. In this paper, we combine CSRL and MSL in order to take advantage of the expressiveness of the former and the usability of the latter. To this aim, we develop a unified notation in which the core logic of MSL is employed to set up the reward structures needed in CSRL, whereas the measure definition mechanism of MSL is exploited to formalize measure and property specification patterns in a componentoriented fashion.
TwoEagles: A Model Transformation Tool from Architectural Descriptions to Queueing Networks
 Proc. 8th European Performance Engineering Workshop
, 2011
"... Abstract. We present the implementation of a methodology for the modeling, analysis, and comparison of software architectures based on their performance characteristics. The implementation is part of a software tool that is called TWOEAGLES, which extends the architecturecentric tool TwoTowers – ba ..."
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Abstract. We present the implementation of a methodology for the modeling, analysis, and comparison of software architectures based on their performance characteristics. The implementation is part of a software tool that is called TWOEAGLES, which extends the architecturecentric tool TwoTowers – based on the stochastic process algebraic description language ÆMILIA – and integrates it into Eclipse. The extension consists of a Javacoded plugin that we have called AEmilia to QN. This plugin transforms ÆMILIA descriptions into queueing network models expressed in the XML schema PMIF, which can then be rendered via the QN Editor tool or analyzed by multiple queueing network solvers that can be invoked through the Weasel web service. 1
On the use of BioPEPA for modelling and analysing collective behaviours in swarm robotics
 SWARM INTELL (2013 ) 7:201–228
, 2013
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