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26
Towards Performance Evaluation with General Distributions in Process Algebras
 in Proc. of the 9th Int. Conf. on Concurrency Theory (CONCUR '98), LNCS 1466:405422
, 1998
"... . We present a process algebra for the performance modeling and evaluation of concurrent systems whose activity durations are expressed through general probability distributions. We first determine the class of generalized semiMarkov processes (GSMPs) as being the class of stochastic processes on w ..."
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Cited by 32 (12 self)
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. We present a process algebra for the performance modeling and evaluation of concurrent systems whose activity durations are expressed through general probability distributions. We first determine the class of generalized semiMarkov processes (GSMPs) as being the class of stochastic processes on which we must rely for performance evaluation to be possible. Then we argue that in this context the right semantics for algebraic terms is a variant of the ST semantics which accounts for both functional and performance aspects. The GSMP based process algebra we propose is introduced together with its formal semantics, an example of performance evaluation, and a notion of probabilistic bisimulation based equivalence accounting for action durations which is shown to be a congruence. 1 Introduction The aim of this paper is to develop a core calculus suitable for the performance evaluation of concurrent systems whose activity durations are expressed through general probability distributions. I...
Twotowers: A Tool Integrating Functional And Performance Analysis Of Concurrent Systems
, 1998
"... We present TwoTowers, a tool for analyzing functional and performance properties of concurrent systems expressed as terms in the stochastically timed reward process algebra EMPA r . TwoTowers builds on two existing tools, CWBNC and MarCA, that have been retargeted to carry out functional and pe ..."
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Cited by 30 (12 self)
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We present TwoTowers, a tool for analyzing functional and performance properties of concurrent systems expressed as terms in the stochastically timed reward process algebra EMPA r . TwoTowers builds on two existing tools, CWBNC and MarCA, that have been retargeted to carry out functional and performance analysis (respectively) of EMPA r system specifications. As an example, we describe the application of TwoTowers to the LehmannRabin randomized distributed algorithm for the dining philosopher problem.
Compositional Analysis of Expected Delays in Networks of Probabilistic I/O Automata
, 1998
"... Probabilistic I/O automata (PIOA) constitute a model for distributed or concurrent systems that incorporates a notion of probabilistic choice. The PIOA model provides a notion of composition, for constructing a PIOA for a composite system from a collection of PIOAs representing the components. We pr ..."
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Cited by 19 (8 self)
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Probabilistic I/O automata (PIOA) constitute a model for distributed or concurrent systems that incorporates a notion of probabilistic choice. The PIOA model provides a notion of composition, for constructing a PIOA for a composite system from a collection of PIOAs representing the components. We present a method for computing completion probability and expected completion time for PIOAs. Our method is compositional, in the sense that it can be applied to a system of PIOAs, one component at a time, without ever calculating the global state space of the system (i.e. the composite PIOA). The method is based on symbolic calculations with vectors and matrices of rational functions, and it draws upon a theory of observables, which are mappings from delayed traces to real numbers that generalize the classical "formal power series " from algebra and combinatorics. Central to the theory is a notion of representation for an observable, which generalizes the clasical notion "linear representation " for formal power series. As in the classical case, the representable observables coincide with an abstractly defined class of "rational" observables; this fact forms the foundation of our method. 1
A processalgebraic language for probabilistic I/O automata
 IN PROC. OF THE 14TH INT. CONF. ON CONCURRENCY THEORY (CONCUR 2003), LNCS
, 2003
"... We present a processalgebraic language for Probabilistic I/O Automata (PIOA). To ensure that PIOA specifications given in our language satisfy the “inputenabled” property, which requires that all input actions be enabled in every state of a PIOA, we augment the language with a set of type inferenc ..."
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Cited by 15 (2 self)
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We present a processalgebraic language for Probabilistic I/O Automata (PIOA). To ensure that PIOA specifications given in our language satisfy the “inputenabled” property, which requires that all input actions be enabled in every state of a PIOA, we augment the language with a set of type inference rules. We also equip our language with a formal operational semantics defined by a set of transition rules. We present a number of results whose thrust is to establish that the typing and transition rules are sensible and interact properly. The central connection between types and transition systems is that if a term is welltyped, then in fact the associated transition system is inputenabled. We also consider two notions of equivalence for our language, weighted bisimulation equivalence and PIOA behavioral equivalence. We show that both equivalences are substitutive with respect to the operators of the language, and note that weighted bisimulation equivalence is a strict refinement of behavioral equivalence.
Comparing the QoS of Internet Audio Mechanisms via Formal Methods
 ACM Transactions on Modelling and Computer Simulation 11(1):142, ACM
, 1980
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Formal Performance Modeling and Evaluation of an Adaptive Mechanism for Packetized Audio over the Internet
 Form. Asp. of Comp
, 1999
"... Abstract. A case study is presented which concerns the design of an adaptive mechanism for packetized audio for use over the Internet. During the design process, the audio mechanism was modeled with the stochastically timed process algebra EMPA and analyzed via simulation by the EMPA based software ..."
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Cited by 9 (6 self)
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Abstract. A case study is presented which concerns the design of an adaptive mechanism for packetized audio for use over the Internet. During the design process, the audio mechanism was modeled with the stochastically timed process algebra EMPA and analyzed via simulation by the EMPA based software tool TwoTowers in order to predict the percentage of packets that are received in time for being played out. The predicted performance figures obtained from the algebraic model illustrated in advance the adequacy of the approach adopted in the design of the audio playout delay control mechanism. Based on these performance figures, it was possible to implement and develop the complete mechanism without incurring in additional costs due to the late discovery of unexpected errors or inefficiency. Performance results obtained from experiments conducted on the field confirmed the predictive simulative results. 1.
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 8 (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.
On Behavior Equivalence for Probabilistic I/O Automata and its Relationship to Probabilistic Bisimulation
 Journal of Automata, Languages, and Combinatorics
, 2003
"... Previous work of the author has developed probabilistic input /output automata (PIOA) as a formalism for modeling systems that exhibit concurrent and probabilistic behavior. Central to that work was the notion of the "behavior map" associated with a state of a PIOA. The present paper p ..."
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Cited by 7 (1 self)
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Previous work of the author has developed probabilistic input /output automata (PIOA) as a formalism for modeling systems that exhibit concurrent and probabilistic behavior. Central to that work was the notion of the "behavior map" associated with a state of a PIOA. The present paper presents a new, simpler definition for PIOA behavior maps, investigates the induced "same behavior map" equivalence relation, and compares it with the standard notion of probabilistic bisimulation equivalence.
Functional And Performance Modeling And Analysis Of Token Ring Using Empa
 in Proc. of 6th Italian Conf. on Theoretical Computer Science, World Scienti
, 1998
"... this paper we shall consider the stochastically timed process algebra ..."
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Cited by 2 (2 self)
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this paper we shall consider the stochastically timed process algebra
A Study about Tradeoff between Performance and Security in an Internet Audio Mechanism
"... We study the nature of the relationship between performance measures and privacy guarantees in the case study of an adaptive protocol for the secure transmission of realtime audio over the Internet. The analysis is conducted on a... ..."
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Cited by 1 (0 self)
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We study the nature of the relationship between performance measures and privacy guarantees in the case study of an adaptive protocol for the secure transmission of realtime audio over the Internet. The analysis is conducted on a...