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142
First Name / family name of the Scientific Coordinator
"... Computational ecology is a recent field whose objective is to construct models of ecological systems (e.g., ecological communities and metapopulations) to gain understanding of the real systems. These models can be analysed with several computational tools to make predictions about the dynamics of ..."
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, stochastic behaviour, nondeterministic behaviour or a combination of the above. Anna Philippou et al. have developed a process calculus, called PALPS, to model spatiallyexplicit ecological systems [1]. My work consisted on building on this work in two directions: (1) I developed a methodology
Weak bisimulation for probabilistic systems
 CONCURRENCY THEORY, LNCS
, 2000
"... In this paper, we introduce weak bisimulation in the framework of Labeled Concurrent Markov Chains, that is, probabilistic transition systems which exhibit both probabilistic and nondeterministic behavior. By resolving the nondeterminism present, these models can be decomposed into a possibly infini ..."
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Cited by 59 (8 self)
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In this paper, we introduce weak bisimulation in the framework of Labeled Concurrent Markov Chains, that is, probabilistic transition systems which exhibit both probabilistic and nondeterministic behavior. By resolving the nondeterminism present, these models can be decomposed into a possibly infinite number of computation trees. We show that in order to compute weak bisimulation it is sufficient to restrict attention to only a finite number of these computations. Finally, we present an algorithm for deciding weak bisimulation which has polynomialtime complexity in the number of states of the transition system.
A GraphTheoretic Network Security Game
 INT. J. AUTONOMOUS AND ADAPTIVE COMMUNICATIONS SYSTEMS
"... ..."
Scalar outcomes suffice for finitary probabilistic testing
 of Lecture Notes in Computer Science
, 2007
"... Abstract. The question of equivalence has long vexed research in concurrency, leading to many different denotational and bisimulationbased approaches; a breakthrough occurred with the insight that tests expressed within the concurrent framework itself, based on a special “success action”, yield ..."
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Cited by 18 (11 self)
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Abstract. The question of equivalence has long vexed research in concurrency, leading to many different denotational and bisimulationbased approaches; a breakthrough occurred with the insight that tests expressed within the concurrent framework itself, based on a special “success action”, yield equivalences that make only inarguable distinctions. When probability was added, however, it seemed necessary to extend the testing framework beyond a direct probabilistic generalisation in order to remain useful. An attractive possibility was the extension to multiple success actions that yielded vectors of realvalued outcomes. Here we prove that such vectors are unnecessary when processes are finitary, that is finitely branching and finitestate: single scalar outcomes are just as powerful. Thus for finitary processes we can retain the original, simpler testing approach and its direct connections to other naturally scalarvalued phenomena. 1
PUB TYPE Collected Works Proceedings (021)
"... The fourth volume of this proceedings contains full research articles. Papers include: (1) "Conceptual and procedural approaches to problemsolving " (Y. MohammadYusof and D. Tall); (2) "Teaching differential equations to chemistry and biology students: An overview on methodology of ..."
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to geometry " (L. Nasser, N. Sant'Anna, and A.P. Sant'Anna); (9) "Solving word problems with different mediators: How do deaf children perform? " (T. Nunes and C. Moreno); (10) "Telling definition and conditions: An ethnomethodological study of sociomathematical activity
Probabilistic resource failure in realtime process algebra
 IN PROCEEDINGS CONCUR 98
, 1998
"... ..."
The Price of Defense
 Proceedings of the 31st International Symposium on Mathematical Foundations of Computer Science
, 2006
"... Abstract. We consider a strategic game with two classes of confronting randomized players on a graph G(V, E): ν attackers, each choosing vertices and wishing to minimize the probability of being caught, and a defender, who chooses edges and gains the expected number of attackers it catches. The Pric ..."
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Cited by 10 (4 self)
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Abstract. We consider a strategic game with two classes of confronting randomized players on a graph G(V, E): ν attackers, each choosing vertices and wishing to minimize the probability of being caught, and a defender, who chooses edges and gains the expected number of attackers it catches. The Price of Defense is the worstcase ratio, over all Nash equilibria, of the optimal gain of the defender over its gain at a Nash equilibrium. We provide a comprehensive collection of tradeoffs between the Price of Defense and the computational efficiency of Nash equilibria. – Through reduction to a TwoPlayers, ConstantSum Game, we prove that a Nash equilibrium can be computed in polynomial time. The reduction does not provide any apparent guarantees on the Price of Defense. – To obtain such, we analyze several structured Nash equilibria: • In a Matching Nash equilibrium, the support of the defender is an Edge Cover. We prove that they can be computed in polynomial
A Network Game with Attacker and Protector Entities
 Proceedings of the 16th Annual International Symposium on Algorithms and Computation
, 2005
"... Consider an information network with harmful procedures called attackers (e.g., viruses); each attacker uses a probability distribution to choose a node of the network to damage. Opponent to the attackers is the system protector scanning and cleaning from attackers some part of the network (e.g., an ..."
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Cited by 11 (8 self)
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Consider an information network with harmful procedures called attackers (e.g., viruses); each attacker uses a probability distribution to choose a node of the network to damage. Opponent to the attackers is the system protector scanning and cleaning from attackers some part of the network (e.g., an edge or a path), which it chooses independently using another probability distribution. Each attacker wishes to maximize the probability of escaping its cleaning by the system protector; towards a conflicting objective, the system protector aims at maximizing the expected number of cleaned attackers. We model this network scenario as a noncooperative strategic game on graphs. We focus on the special case where the protector chooses a single edge. We are interested in the associated Nash equilibria, where no network entity can unilaterally improve its local objective. We obtain the following results: • No instance of the game possesses a pure Nash equilibrium. • Every mixed Nash equilibrium enjoys a graphtheoretic structure, which enables a (typically exponential) algorithm to compute it.
A General Resource Framework for RealTime Systems
 In Proceedings of RISSEF’02, pages 234–248, LNCS 2941
, 2002
"... A General Resource Framework for RealTime Systems The paper describes a formal framework for designing and reasoning about resourceconstrained systems. The framework is based on a series of process algebraic formalisms which have been previously developed to describe and analyze various aspects of ..."
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Cited by 9 (4 self)
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A General Resource Framework for RealTime Systems The paper describes a formal framework for designing and reasoning about resourceconstrained systems. The framework is based on a series of process algebraic formalisms which have been previously developed to describe and analyze various aspects of realtime communicating, concurrent systems. We develop a uniform framework for formal treatment of resources and demonstrate how previous work fits into the new framework.
Modeling and analysis of poweraware systems
 Proceedings of TACAS ’03, volume 2619 of LNCS
, 2003
"... Abstract. The paper describes a formal approach for designing and reasoning about powerconstrained, timed systems. The framework is based on process algebra, a formalism that has been developed to describe and analyze communicating concurrent systems. The proposed extension allows the modeling of ..."
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Cited by 11 (5 self)
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Abstract. The paper describes a formal approach for designing and reasoning about powerconstrained, timed systems. The framework is based on process algebra, a formalism that has been developed to describe and analyze communicating concurrent systems. The proposed extension allows the modeling of probabilistic resource failures, priorities of resource usages, and power consumption by resources within the same formalism. Thus, it is possible to model alternative powerconsumption behaviors and analyze tradeoffs in their timing and other characteristics. This paper describes the modeling and analysis techniques, and illustrates them with examples, including a dynamic voltagescaling algorithm. 1
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