Results 1  10
of
79
The Algebra of Timed Processes ATP: Theory and Application
 INFORMATION AND COMPUTATION
, 1994
"... We study a process algebra ATP for the description and analysis of systems of timed processes. An important feature of the algebra is that its vocabulary of actions contains a distinguished element . An occurrence of is a time event representing progress of time. The algebra has, apart from standar ..."
Abstract

Cited by 105 (4 self)
 Add to MetaCart
We study a process algebra ATP for the description and analysis of systems of timed processes. An important feature of the algebra is that its vocabulary of actions contains a distinguished element . An occurrence of is a time event representing progress of time. The algebra has, apart from standard operators of process algebras like CCS or ACP, a primitive binary unitdelay operator. For two arguments, processes P and Q, this operator gives a process which behaves as P if started before the occurrence of a time action and as Q otherwise. From this operator we define dunit delay operators that can model delay constructs of languages, like timeouts or watchdogs. The use of such operators is illustrated by examples. ATP is provided with a complete axiomatisation with respect to strong bisimulation semantics. It is shown that the algebras obtained by adding the various dunit delay operators to ATP are conservative extensions of it.
Algebraic Reasoning for Probabilistic Concurrent Systems
 Proc. IFIP TC2 Working Conference on Programming Concepts and Methods
, 1990
"... We extend Milner's SCCS to obtain a calculus, PCCS, for reasoning about communicating probabilistic processes. In particular, the nondeterministic process summation operator of SCCS is replaced with a probabilistic one, in which the probability of behaving like a particular summand is given explicit ..."
Abstract

Cited by 94 (5 self)
 Add to MetaCart
We extend Milner's SCCS to obtain a calculus, PCCS, for reasoning about communicating probabilistic processes. In particular, the nondeterministic process summation operator of SCCS is replaced with a probabilistic one, in which the probability of behaving like a particular summand is given explicitly. The operational semantics for PCCS is based on the notion of probabilistic derivation, and is given structurally as a set of inference rules. We then present an equational theory for PCCS based on probabilistic bisimulation, an extension of Milner's bisimulation proposed by Larsen and Skou. We provide the first axiomatization of probabilistic bisimulation, a subset of which is relatively complete for finitestate probabilistic processes. In the probabilistic case, a notion of processes with almost identical behavior (i.e., with probability 1 \Gamma ffl, for ffl sufficiently small) appears to be more useful in practice than a notion of equivalence, since the latter is often too restricti...
An Efficiency Preorder for Processes
"... A simple efficiency preorder for CCS processes is introduced, in which p ! q means that q is at least as fast as p, or more generally, p uses at least as much resources as q. It is shown to be preserved by all CCS contexts except summation and it is used to analyse a nontrivial example: differe ..."
Abstract

Cited by 69 (10 self)
 Add to MetaCart
A simple efficiency preorder for CCS processes is introduced, in which p ! q means that q is at least as fast as p, or more generally, p uses at least as much resources as q. It is shown to be preserved by all CCS contexts except summation and it is used to analyse a nontrivial example: different implementations of a bounded buffer. Finally a sound and complete proof system for finite processes is given. This paper appeared earlier in [1] and [2]. This version of the paper has been revised, corrected and extended to include more operators, more examples and some additional remarks and observations by the first author. Hence all errors are entirely his responsiblity. Most of this work was done while the first author was at the University of Sussex and supported by SERC grant GR/D 97368 of the Science and Engineering Research Council of Great Britain. y The second author would like to acknowledge the support of ESPIRIT II. 1 Introduction A large number of behavioural equivale...
Modal and Temporal Logics for Processes
, 1996
"... this paper have been presented at the 4th European Summer School in Logic, Language and Information, University of Essex, 1992; at the Tempus Summer School for Algebraic and Categorical Methods in Computer Science, Masaryk University, Brno, 1993; and the Summer School in Logic Methods in Concurrency ..."
Abstract

Cited by 69 (2 self)
 Add to MetaCart
this paper have been presented at the 4th European Summer School in Logic, Language and Information, University of Essex, 1992; at the Tempus Summer School for Algebraic and Categorical Methods in Computer Science, Masaryk University, Brno, 1993; and the Summer School in Logic Methods in Concurrency, Aarhus University, 1993. I would like to thank the organisers and the participants of these summer schools, and of the Banff higher order workshop. I would also like to thank Julian Bradfield for use of his Tex tree constructor for building derivation trees and Carron Kirkwood, Faron Moller, Perdita Stevens and David Walker for comments on earlier drafts.
A Calculus of Broadcasting Systems
 SCIENCE OF COMPUTER PROGRAMMING
, 1991
"... CBS is a simple and natural CCSlike calculus where processes speak one at a time and are heard instantaneously by all others. Speech is autonomous, contention between speakers being resolved nondeterministically, but hearing only happens when someone else speaks. Observationally meaningful laws dif ..."
Abstract

Cited by 62 (8 self)
 Add to MetaCart
CBS is a simple and natural CCSlike calculus where processes speak one at a time and are heard instantaneously by all others. Speech is autonomous, contention between speakers being resolved nondeterministically, but hearing only happens when someone else speaks. Observationally meaningful laws differ from those of CCS. The change from handshake communication in CCS to broadcast in CBS permits several advances. (1) Priority, which attaches only to autonomous actions, is simply added to CBS in contrast to CCS, where such actions are the result of communication. (2) A CBS simulator runs a process by returning a list of values it broadcasts. This permits a powerful combination, CBS with the host language. It yields several elegant algorithms. Only processes with a unique response to each input are needed in practice, so weak bisimulation is a congruence. (3) CBS subsystems are interfaced by translators; by mapping messages to silence, these can restrict hearing and hide speech. Reversi...
A Process Algebra of Communicating Shared Resources with Dense Time and Priorities
 THEORETICAL COMPUTER SCIENCE
, 1997
"... ..."
Extended Markovian Process Algebra
, 1996
"... . EMPA enhances the expressiveness of classical process algebras by integrating functional and performance descriptions of concurrent systems. This is achieved by offering, besides passive actions (useful for pure nondeterminism), actions whose duration is exponentially distributed as well as immedi ..."
Abstract

Cited by 43 (4 self)
 Add to MetaCart
. EMPA enhances the expressiveness of classical process algebras by integrating functional and performance descriptions of concurrent systems. This is achieved by offering, besides passive actions (useful for pure nondeterminism), actions whose duration is exponentially distributed as well as immediate actions (useful for performance abstraction), parametrized by priority levels (hence prioritized choices) and weights (hence probabilistic choices). In order to analyze an EMPA term, from its integrated semantic model (a transition system labeled on both action types and action durations) we derive a functional semantic model (a transition system labeled on action types only) and a performance semantic model (a Markov chain). We show that an integrated analysis, i.e. a notion of equivalence on the integrated semantic model, is not only convenient but also necessary to achieve compositionality. 1 Introduction The need of integrating the performance modeling and analysis of a concurrent s...
An algebraic framework for urgency
 Information and Computation
, 2000
"... Timed formalisms are extensions of untimed ones by adding clocks, realvalued ..."
Abstract

Cited by 37 (6 self)
 Add to MetaCart
Timed formalisms are extensions of untimed ones by adding clocks, realvalued
Causality for Mobile Processes
 In Proceedings of ICALP'95, LNCS 944
, 1995
"... Abstract. We study causality in the ßcalculus. Our notion of causality combines the dependencies given by the syntactic structure of processes with those originated by passing names. It turns out that two transitions not causally related may although occur in a fixed ordering in any computation, i. ..."
Abstract

Cited by 29 (18 self)
 Add to MetaCart
Abstract. We study causality in the ßcalculus. Our notion of causality combines the dependencies given by the syntactic structure of processes with those originated by passing names. It turns out that two transitions not causally related may although occur in a fixed ordering in any computation, i.e., ßcalculus may express implicitly a priority between actions. Our causality relation still induces the same partial order of transitions for all the computations that are obtained by shuffling transitions that are concurrent (= related neither by causality nor by priority). The presentation takes advantage from a parametric definition of process behaviour that highlights the essence of the topic. All the results on bisimulation based equivalences, congruences, axiomatizations and logics are taken (almost) for free from the interleaving theory. 1 Introduction The study of the behaviour of a distributed system may benefit from knowledge on the causal relation between its events. For examp...
Probabilistic and Prioritized Models of Timed CSP
 Theoretical Computer Science
, 1995
"... In this paper we present two languages that are refinements of timed CSP [4]: a probabilistic language, and a fully deterministic language with a notion of priority. In the first part of the paper we describe the deterministic language and its semantic model. The syntax is based upon that of timed C ..."
Abstract

Cited by 26 (1 self)
 Add to MetaCart
In this paper we present two languages that are refinements of timed CSP [4]: a probabilistic language, and a fully deterministic language with a notion of priority. In the first part of the paper we describe the deterministic language and its semantic model. The syntax is based upon that of timed CSP except some of the operators are refined so as to remove all nondeterminism; this produces prioritized operators. The semantics for our language represents a process as the set of possible behaviours for the process, where a behaviour models the priorities for different actions. A number of algebraic laws for our language are given and the model is illustrated with two examples. In the second part of the paper, we extend the language by adding a probabilistic choice operator. We produce a semantic model for our language which gives the probabilities of different behaviours occurring, as well as modelling the relative priorities for events within a behaviour. The model is illustrated with ...