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370
Relations in Concurrency
"... The theme of this paper is profunctors, and their centrality and ubiquity in understanding concurrent computation. Profunctors (a.k.a. distributors, or bimodules) are a generalisation of relations to categories. Here they are first presented and motivated via spans of event structures, and the seman ..."
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Cited by 304 (36 self)
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The theme of this paper is profunctors, and their centrality and ubiquity in understanding concurrent computation. Profunctors (a.k.a. distributors, or bimodules) are a generalisation of relations to categories. Here they are first presented and motivated via spans of event structures, and the semantics of nondeterministic dataflow. Profunctors are shown to play a key role in relating models for concurrency and to support an interpretation as higherorder processes (where input and output may be processes). Two recent directions of research are described. One is concerned with a language and computational interpretation for profunctors. This addresses the duality between input and output in profunctors. The other is to investigate general spans of event structures (the spans can be viewed as special profunctors) to give causal semantics to higherorder processes. For this it is useful to generalise event structures to allow events which “persist.”
Deriving Bisimulation Congruences for Reactive Systems
 In Proc. of CONCUR 2000, 2000. LNCS 1877
, 2000
"... . The dynamics of reactive systems, e.g. CCS, has often been de ned using a labelled transition system (LTS). More recently it has become natural in de ning dynamics to use reaction rules  i.e. unlabelled transition rules  together with a structural congruence. But LTSs lead more naturally to beha ..."
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Cited by 136 (13 self)
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. The dynamics of reactive systems, e.g. CCS, has often been de ned using a labelled transition system (LTS). More recently it has become natural in de ning dynamics to use reaction rules  i.e. unlabelled transition rules  together with a structural congruence. But LTSs lead more naturally to behavioural equivalences. So one would like to derive from reaction rules a suitable LTS. This paper shows how to derive an LTS for a wide range of reactive systems. A label for an agent a is de ned to be any context F which intuitively is just large enough so that the agent Fa (\a in context F ") is able to perform a reaction. The key contribution of this paper is a precise de nition of \just large enough", in terms of the categorical notion of relative pushout (RPO), which ensures that bisimilarity is a congruence when sucient RPOs exist. Two examples  a simpli ed form of action calculi and termrewriting  are given, for which it is shown that su cient RPOs indeed exist. The thrust of thi...
Decidability Issues for Petri Nets  a survey
, 1994
"... : We survey 25 years of research on decidability issues for Petri nets. We collect results on the decidability of important properties, equivalence notions, and temporal logics. 1. Introduction Petri nets are one of the most popular formal models for the representation and analysis of parallel proc ..."
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Cited by 121 (5 self)
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: We survey 25 years of research on decidability issues for Petri nets. We collect results on the decidability of important properties, equivalence notions, and temporal logics. 1. Introduction Petri nets are one of the most popular formal models for the representation and analysis of parallel processes. They are due to C.A. Petri, who introduced them in his doctoral dissertation in 1962. Some years later, and independently from Petri's work, Karp and Miller introduced vector addition systems [47], a simple mathematical structure which they used to analyse the properties of "parallel program schemata', a model for parallel computation. In their seminal paper on parallel program schemata, Karp and Miller studied some decidability issues for vector addition systems, and the topic continued to be investigated by other researchers. When Petri's ideas reached the States around 1970, it was observed that Petri nets and vector addition systems were mathematically equivalent, even though thei...
Turning SOS Rules into Equations
, 1994
"... Many process algebras are defined by structural operational semantics (SOS). Indeed, most such definitions are nicely structured and fit the GSOS format of [15]. We give a procedure for converting any GSOS language definition to a finite complete equational axiom system (possibly with one infinit ..."
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Cited by 97 (23 self)
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Many process algebras are defined by structural operational semantics (SOS). Indeed, most such definitions are nicely structured and fit the GSOS format of [15]. We give a procedure for converting any GSOS language definition to a finite complete equational axiom system (possibly with one infinitary induction principle) which precisely characterizes strong bisimulation of processes.
Fair testing
 Concur ’95: Concurrency Theory, volume 962 of Lecture Notes in Computer Science
, 1995
"... In this paper we present a solution to the longstanding problem of characterising the coarsest livenesspreserving precongruence with respect to a full (TCSPinspired) process algebra. In fact, we present two distinct characterisations, which give rise to the same relation: an operational one base ..."
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Cited by 96 (2 self)
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In this paper we present a solution to the longstanding problem of characterising the coarsest livenesspreserving precongruence with respect to a full (TCSPinspired) process algebra. In fact, we present two distinct characterisations, which give rise to the same relation: an operational one based on a De NicolaHennessylike testing modality which we call shouldtesting, and a denotational one based on a refined notion of failures. One of the distinguishing characteristics of the shouldtesting precongruence is that it abstracts from divergences in the same way as Milner’s observation congruence, and as a consequence is strictly coarser than observation congruence. In other words, shouldtesting has a builtin fairness assumption. This is in itself a property long soughtafter; it is in notable contrast to the wellknown musttesting of De Nicola and Hennessy (denotationally characterised by a combination of failures and divergences), which treats divergence as catrastrophic and hence is incompatible with observation congruence. Due to these characteristics, shouldtesting supports modular reasoning and allows to use the proof techniques of observation congruence, but also supports additional laws and techniques.
On the Expressive Completeness of the Propositional MuCalculus With Respect to Monadic Second Order Logic
, 1996
"... . Monadic second order logic (MSOL) over transition systems is considered. It is shown that every formula of MSOL which does not distinguish between bisimilar models is equivalent to a formula of the propositional calculus. This expressive completeness result implies that every logic over tran ..."
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Cited by 91 (5 self)
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. Monadic second order logic (MSOL) over transition systems is considered. It is shown that every formula of MSOL which does not distinguish between bisimilar models is equivalent to a formula of the propositional calculus. This expressive completeness result implies that every logic over transition systems invariant under bisimulation and translatable into MSOL can be also translated into the calculus. This gives a precise meaning to the statement that most propositional logics of programs can be translated into the calculus. 1 Introduction Transition systems are structures consisting of a nonempty set of states, a set of unary relations describing properties of states and a set of binary relations describing transitions between states. It was advocated by many authors [26, 3] that this kind of structures provide a good framework for describing behaviour of programs (or program schemes), or even more generally, engineering systems, provided their evolution in time is disc...
Verification on Infinite Structures
, 2000
"... In this chapter, we present a hierarchy of infinitestate systems based on the primitive operations of sequential and parallel composition; the hierarchy includes a variety of commonlystudied classes of systems such as contextfree and pushdown automata, and Petri net processes. We then examine the ..."
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Cited by 90 (2 self)
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In this chapter, we present a hierarchy of infinitestate systems based on the primitive operations of sequential and parallel composition; the hierarchy includes a variety of commonlystudied classes of systems such as contextfree and pushdown automata, and Petri net processes. We then examine the equivalence and regularity checking problems for these classes, with special emphasis on bisimulation equivalence, stressing the structural techniques which have been devised for solving these problems. Finally, we explore the model checking problem over these classes with respect to various linear and branchingtime temporal logics.
On Structured Workflow Modelling
"... Recent years have seen the introduction of many commercial workflow management systems. While there are similarities between the languages of various of these systems, there are also significant differences. One particular area of differences is caused by the fact that di erent systems impose differ ..."
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Cited by 87 (15 self)
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Recent years have seen the introduction of many commercial workflow management systems. While there are similarities between the languages of various of these systems, there are also significant differences. One particular area of differences is caused by the fact that di erent systems impose different syntactic restrictions. For example, some work ow management systems do not allow the use of arbitrary loops. In such cases, business analysts have to choose between either conforming to the language in their speci cations or transforming these speci cations afterwards. The latter option is preferable as this allows for a separation of concerns. In this paper we investigate to what extent such transformations are possible in the context of various syntactical restrictions (the most restrictive of which will be referred to as structured workflows). We also provide a deep insight into the consequences, particularly in terms of expressive power, of imposing such restrictions.
A brief history of process algebra
 THEOR. COMPUT. SCI
, 2004
"... This note addresses the history of process algebra as an area of research in concurrency theory, the theory of parallel and distributed systems in computer science. Origins are traced back to the early seventies of the twentieth century, and developments since that time are sketched. The author giv ..."
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Cited by 83 (1 self)
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This note addresses the history of process algebra as an area of research in concurrency theory, the theory of parallel and distributed systems in computer science. Origins are traced back to the early seventies of the twentieth century, and developments since that time are sketched. The author gives his personal views on these matters. He also considers the present situation, and states some challenges for the future.