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Metrics for Labelled Markov Systems
, 2001
"... The notion of process equivalence of probabilistic processes is sensitive to the exact probabilities of transitions. Thus, a slight change in the transition probabilities will result in two equivalent processes being deemed no longer equivalent. This instability is due to the quantitative nature of ..."
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Cited by 50 (10 self)
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The notion of process equivalence of probabilistic processes is sensitive to the exact probabilities of transitions. Thus, a slight change in the transition probabilities will result in two equivalent processes being deemed no longer equivalent. This instability is due to the quantitative nature of probabilistic processes. In a situation where the process behaviour has a quantitative aspect there should be a more robust approach to process equivalence. This paper studies a metric between labelled Markov processes. This metric has the property that processes are at zero distance if and only if they are bisimilar. The metric is inspired by earlier work on logics for characterizing bisimulation and is related, in spirit, to the Hutchinson metric.
Stochastic processes as concurrent constraint programs
 In Symposium on Principles of Programming Languages
, 1999
"... ) Vineet Gupta Radha Jagadeesan Prakash Panangaden y vgupta@mail.arc.nasa.gov radha@cs.luc.edu prakash@cs.mcgill.ca Caelum Research Corporation Dept. of Math. and Computer Sciences School of Computer Science NASA Ames Research Center Loyola UniversityLake Shore Campus McGill University Moffe ..."
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Cited by 33 (1 self)
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) Vineet Gupta Radha Jagadeesan Prakash Panangaden y vgupta@mail.arc.nasa.gov radha@cs.luc.edu prakash@cs.mcgill.ca Caelum Research Corporation Dept. of Math. and Computer Sciences School of Computer Science NASA Ames Research Center Loyola UniversityLake Shore Campus McGill University Moffett Field CA 94035, USA Chicago IL 60626, USA Montreal, Quebec, Canada Abstract This paper describes a stochastic concurrent constraint language for the description and programming of concurrent probabilistic systems. The language can be viewed both as a calculus for describing and reasoning about stochastic processes and as an executable language for simulating stochastic processes. In this language programs encode probability distributions over (potentially infinite) sets of objects. We illustrate the subtleties that arise from the interaction of constraints, random choice and recursion. We describe operational semantics of these programs (programs are run by sampling random choices), deno...
A Formal Approach to the Integration of Performance Aspects in the Modeling and Analysis of Concurrent Systems
 Information and Computation
, 1998
"... A formal approach for modeling and analyzing concurrent systems is proposed which integrates performance characteristics in the early stages of the design process. The approach relies on both stochastically timed process algebras and stochastically timed Petri nets in order to exploit their compleme ..."
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Cited by 29 (13 self)
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A formal approach for modeling and analyzing concurrent systems is proposed which integrates performance characteristics in the early stages of the design process. The approach relies on both stochastically timed process algebras and stochastically timed Petri nets in order to exploit their complementary advantages. The approach is instantiated to the case of EMPA (Extended Markovian Process Algebra), introduced together with the collection of its four semantics and the notion of equivalence that are required in order to implement the approach. Finally, the case study of the alternating bit protocol is presented to illustrate the adequacy of the approach. 1
Probabilistic Concurrent Constraint Programming
 In Proceedings of CONCUR 97
, 1997
"... . We extend cc to allow the specification of a discrete probability distribution for random variables. We demonstrate the expressiveness of pcc by synthesizing combinators for default reasoning. We extend pcc uniformly over time, to get a synchronous reactive probabilistic programming language, Time ..."
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Cited by 22 (0 self)
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. We extend cc to allow the specification of a discrete probability distribution for random variables. We demonstrate the expressiveness of pcc by synthesizing combinators for default reasoning. We extend pcc uniformly over time, to get a synchronous reactive probabilistic programming language, Timed pcc. We describe operational and denotational models for pcc (and Timed pcc). The key feature of the denotational model(s) is that parallel composition is essentially set intersection. We show that the denotational model of pcc (resp. Timed pcc) is conservative over cc (resp. tcc). We also show that the denotational models are fully abstract for an operational semantics that records probability information. 1 Introduction Concurrent constraint programming(CCP, [Sar93]) is an approach to computation which uses constraints for the compositional specification of concurrent systems. It replaces the traditional notion of a store as a valuation of variables with the notion of a store as a cons...
Structural Techniques and Performance Bounds of Stochastic Petri Net Models
 Advances in Petri Nets 1992, volume 609 of Lecture Notes in Computer Science
, 1992
"... In this paper we overview some recent results obtained by the authors and collaborators on the performance bounds analysis of some stochastic Petri net systems. The mathematical model can be seen either as a result of the addition of a particular random timing interpretation to an "autonomou ..."
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Cited by 21 (10 self)
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In this paper we overview some recent results obtained by the authors and collaborators on the performance bounds analysis of some stochastic Petri net systems. The mathematical model can be seen either as a result of the addition of a particular random timing interpretation to an "autonomous" Petri net or as a generalization of classical queueing networks with the addendum of a general synchronization primitive. It constitutes an adequate tool for both the validation of logical properties and the evaluation of performance measures of concurrent and distributed systems. Qualitative and quantitative understandings of Petri net models are stressed here making special emphasis on structural techniques for the analysis of logical and performance properties. Important aspects from the performance point of view, such as relative throughput of stations (transitions), and number of servers present at them, are related to Petri net concepts like P or Tsemiflows or liveness bounds...
Dynamic QoS Management and Optimisation in ServiceBased Systems
"... Servicebased systems that are dynamically composed at run time to provide complex, adaptive functionality are currently one of the main development paradigms in software engineering. However, the Quality of Service (QoS) delivered by these systems remains an important concern, and needs to be mana ..."
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Cited by 18 (13 self)
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Servicebased systems that are dynamically composed at run time to provide complex, adaptive functionality are currently one of the main development paradigms in software engineering. However, the Quality of Service (QoS) delivered by these systems remains an important concern, and needs to be managed in an equally adaptive and predictable way. To address this need, we introduce a novel, toolsupported framework for the development of adaptive servicebased systems called QoSMOS (QoS Management and Optimisation of Servicebased systems). QoSMOS can be used to develop servicebased systems that achieve their QoS requirements through dynamically adapting to changes in the system state, environment and workload. QoSMOS servicebased systems translate highlevel QoS requirements specified by their administrators into probabilistic temporal logic formulae, which are then formally and automatically analysed to identify and enforce optimal system configurations. The QoSMOS selfadaptation mechanism can handle reliability and performancerelated QoS requirements, and can be integrated into newly developed solutions or legacy systems. The effectiveness and scalability of the approach are validated using simulations and a set of experiments based on an implementation of an adaptive servicebased system for remote medical assistance.
Modeling and Analyzing Concurrent Systems with MPA
 Proc. of 2nd Process Algebra and Performance Modelling Workshop
, 1994
"... Process algebras are one of the main tools for modeling and analyzing concurrent systems. However, they can be used to describe only the functional aspect of system behavior. Recently, the relevance of integrating performance evaluation within the process of specification, design and implementation ..."
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Cited by 18 (2 self)
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Process algebras are one of the main tools for modeling and analyzing concurrent systems. However, they can be used to describe only the functional aspect of system behavior. Recently, the relevance of integrating performance evaluation within the process of specification, design and implementation of concurrent systems has been widely recognized. Hence, an effort has been made in order to handle also the temporal aspect of system behavior. In this paper the stochastic process algebra MPA (Markovian Process Algebra) is briefly introduced, together with its operational interleaving semantics, its markovian semantics and its operational net semantics. A concurrent system is described as a term of MPA. The operational interleaving semantics (defined by following Plotkin's structured operational semantics approach, augmented with two transformations) associates a labeled transition system with each MPA term. The markovian semantics is defined through an algorithm which transforms labeled t...
Efficient Simulation of THOR Nets
"... . The aim of our project is to develop and implement an efficient modeling technique and methods for a fast sequential and distributed simulation of realtime systems, such as assembly lines, industrial control systems, or communication protocols. Our simulation language developed to build models of ..."
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Cited by 16 (6 self)
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. The aim of our project is to develop and implement an efficient modeling technique and methods for a fast sequential and distributed simulation of realtime systems, such as assembly lines, industrial control systems, or communication protocols. Our simulation language developed to build models of these systems is a class of highlevel Petri nets which allows complex objects for token values and provides different kinds of timing aspects as well as an appropriate structuring mechanism for nets. We call this kind of highlevel Petri nets Thorns (Timed Hierarchical ObjectRelated Nets). A problem in simulating any kind of models is the considerable amount of time necessary for the execution of large or complex systems models. In our project we face this problem by developing and implementing special methods for an efficient distributed simulator. The main idea is to derive these methods from the optimistic approach in the theory of distributed simulation of discrete event systems. To...
On the Performance of Synchronized Programs in Distributed Networks with Random Processing Times and Transmission Delays
, 1994
"... A synchronizer is a compiler that transforms a program designed to run in a synchronous network into a program that runs in an asynchronous network. The behavior of a simple synchronizer, which also represents a basic mechanism for distributed computing and for the analysis of marked graphs, was stu ..."
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Cited by 15 (2 self)
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A synchronizer is a compiler that transforms a program designed to run in a synchronous network into a program that runs in an asynchronous network. The behavior of a simple synchronizer, which also represents a basic mechanism for distributed computing and for the analysis of marked graphs, was studied in [ER1] and [ER2] under the assumption that message transmission delays and processing times are constant. In this paper we study the behavior of the simple synchronizer when processing times and transmission delays are random. Our main performance measure is the rate of a network, i.e., the average number of computational steps executed by a processor in the network, per unit time. We analyze the effect of the topology and the probability distributions of the random variables on the behavior of the network. For random variables with exponential distribution we provide tight (i.e. attainable) bounds and study the effect of a bottleneck processor on the rate. Keywords: Distributed Netwo...
Token Ring Arbiters: An Exercise in Asynchronous Logic Design with Petri Nets
, 1995
"... Designing an asynchronous communication architecture in a VLSI system, we have the choice of either using a token ring or a bus. The token ring structure is often more reliable than the bus structure because of its pointtopoint interconnection. In this paper, we study two alternative token ring ar ..."
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Cited by 12 (5 self)
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Designing an asynchronous communication architecture in a VLSI system, we have the choice of either using a token ring or a bus. The token ring structure is often more reliable than the bus structure because of its pointtopoint interconnection. In this paper, we study two alternative token ring arbitration protocols which we call Busy Ring Protocol (BRP) and Lazy Ring Protocol (LRP). Their performance evaluation shows that BRP allows better response time under higher request rates, while its major disadvantage is waste of activity, and hence power, if the request traffic is relatively low. We describe the design of speedindependent control circuits for these two ring protocols. The initial specification of the protocol made in a Petri net is refined to a Signal Transition Graph, which is further implemented into a logical circuit by recently developed methods. The logical circuit involves, as a standard component, a twoway mutual exclusion (ME) element. The arbiter designs have be...