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Resource Access Control in Systems of Mobile Agents
 Information and Computation
, 1998
"... INTRODUCTION Mobile computation, where independent agents roam widely distributed networks in search of resources and information, is fast becoming a reality. A number of programming languages, APIs and protocols have recently emerged which seek to provide highlevel support for mobile agents. These ..."
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Cited by 201 (19 self)
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INTRODUCTION Mobile computation, where independent agents roam widely distributed networks in search of resources and information, is fast becoming a reality. A number of programming languages, APIs and protocols have recently emerged which seek to provide highlevel support for mobile agents. These include Java [30], Odyssey [15], Aglets [19], Voyager [24] and the latest revisions of the Internet protocol [25, 2]. In addition to these commercial efforts, many prototype languages have been developed and implemented within the programming language research community  examples include Linda [8, 9], Facile [16], Obliq [7], Infospheres [11], the join calculus [13], and Nomadic Pict [33]. In this paper we address the issue of resource access control for such languages. Central to the paradigm of mobile computation are the notions of agent, resource and location. Agents are effective entities that perform computation and interact with other First publis
Language primitives and type discipline for structured communicationbased programming
 In ESOP’98, volume 1381 of LNCS
, 1998
"... Session primitives and types provide a flexible programming style for structured interaction, and are used to statically check the safe and consistent composition of protocols in communicationcentric distributed software. Unfortunately authors working on session types have recently realised that so ..."
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Cited by 199 (47 self)
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Session primitives and types provide a flexible programming style for structured interaction, and are used to statically check the safe and consistent composition of protocols in communicationcentric distributed software. Unfortunately authors working on session types have recently realised that some of the previously published systems fail to satisfy the basic theorems of Subject Reduction and Type Safety. This report discusses the issues involved in higherorder session communication, presents a formulation of the recursive types as well as proofs of the Subject Reduction and Type Safety Theorems of the original session typing system by HondaVasconcelosKubo in ESOP’98. It also proposes a variant which allows a more liberal higherorder session communication, based on an idea of Gay and Hole.
A Calculus of Mobile Processes, Part I
 I AND II. INFORMATION AND COMPUTATION
, 1989
"... We present the ßcalculus, a calculus of communicating systems in which one can naturally express processes which have changing structure. Not only may the component agents of a system be arbitrarily linked, but a communication between neighbours may carry information which changes that linkage. The ..."
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Cited by 189 (3 self)
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We present the ßcalculus, a calculus of communicating systems in which one can naturally express processes which have changing structure. Not only may the component agents of a system be arbitrarily linked, but a communication between neighbours may carry information which changes that linkage. The calculus is an extension of the process algebra CCS, following work by Engberg and Nielsen who added mobility to CCS while preserving its algebraic properties. The ßcalculus gains simplicity by removing all distinction between variables and constants; communication links are identified by names, and computation is represented purely as the communication of names across links. After an illustrated description of how the ßcalculus generalises conventional process algebras in treating mobility, several examples exploiting mobility are given in some detail. The important examples are the encoding into the ß calculus of higherorder functions (the calculus and combinatory algebra), the tr...
On reductionbased process semantics
 Theoretical Computer Science
, 1995
"... Abstract. A formulation of semantic theories for processes which is based on reduction relation and equational reasoning is studied. The new construction can induce meaningful theories for processes, both in strong and weak settings. The resulting theories in many cases coincide with, and sometimes ..."
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Cited by 144 (21 self)
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Abstract. A formulation of semantic theories for processes which is based on reduction relation and equational reasoning is studied. The new construction can induce meaningful theories for processes, both in strong and weak settings. The resulting theories in many cases coincide with, and sometimes generalise, observationbased formulation of behavioural equivalence. The basic construction of reductionbased theories is studied, taking a simple name passing calculus called \nucalculus as an example. Results on other calculi are also briefly discussed.
Hierarchical Finite State Machines with Multiple Concurrency Models
 IEEE Transactions on Computeraided Design of Integrated Circuits and Systems
, 1999
"... This paper studies the semantics of hierarchical finite state machines (FMS's) that are composed using various concurrency models, particularly dataflow, discreteevents, and synchronous/reactive modeling. It is argued that all three combinations are useful, and that the concurrency model can be sel ..."
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Cited by 115 (36 self)
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This paper studies the semantics of hierarchical finite state machines (FMS's) that are composed using various concurrency models, particularly dataflow, discreteevents, and synchronous/reactive modeling. It is argued that all three combinations are useful, and that the concurrency model can be selected independently of the decision to use hierarchical FSM's. In contrast, most formalisms that combine FSM's with concurrency models, such as Statecharts (and its variants) and hybrid systems, tightly integrate the FSM semantics with the concurrency semantics. An implementation that supports three combinations is described.
An Interactionbased Language and its Typing System
 In PARLE’94, volume 817 of LNCS
, 1994
"... We present a small language L and its typing system based on the idea of interaction, one of the important notions in parallel and distributed computing. L is based on, apart from such constructs as parallel composition and process creation, three pairs of communication primitives which use the noti ..."
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Cited by 109 (17 self)
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We present a small language L and its typing system based on the idea of interaction, one of the important notions in parallel and distributed computing. L is based on, apart from such constructs as parallel composition and process creation, three pairs of communication primitives which use the notion of a session, a semantically atomic chain of communication actions which can interleave with other such chains freely, for highlevel abstraction of interactionbased computing. Three primitives enable programmers to elegantly describe complex interactions among processes with a rigorous type discipline similar to ML [4]. The language is given formal operational semantics and a type inference system, regarding which we prove that if a program is welltyped in the typing system, it never causes runtime error due to type inconsistent communication patterns, offering a new foundation for type discipline in parallel programming languages. 1 Introduction The idea of interaction, that is, rec...
The Fusion Calculus: Expressiveness and Symmetry in Mobile Processes (Extended Abstract)
 LICS'98
, 1998
"... We present the fusion calculus as a significant step towards a canonical calculus of concurrency. It simplifies and extends the πcalculus.
The fusion calculus contains the polyadic πcalculus as a proper subcalculus and thus inherits all its expressive power. The gain is that fusion contains action ..."
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Cited by 108 (13 self)
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We present the fusion calculus as a significant step towards a canonical calculus of concurrency. It simplifies and extends the πcalculus.
The fusion calculus contains the polyadic πcalculus as a proper subcalculus and thus inherits all its expressive power. The gain is that fusion contains actions akin to updating a shared state, and a scoping construct for bounding their effects. Therefore it is easier to represent computational models such as concurrent constraints formalisms. It is also easy to represent the so called strong reduction strategies in the lambdacalculus, involving reduction under abstraction. In the πcalculus these tasks require elaborate encodings.
The dramatic main point of this paper is that we achieve these improvements by simplifying the πcalculus rather than adding features to it. The fusion calculus has only one binding operator where the πcalculus has two (input and restriction). It has a complete symmetry between input and output actions where the πcalculus has not. There is only one sensible variety of bisimulation congruence where the picalculus has at least three (early, late and open). Proofs about the fusion calculus, for example in complete axiomatizations and full abstraction, therefore are shorter and clearer.
Our results on the fusion calculus in this paper are the following. We give a structured operational semantics in the traditional style. The novelty lies in a new kind of action, fusion actions for emulating updates of a shared state. We prove that the calculus contains the πcalculus as a subcalculus. We define and motivate the bisimulation equivalence and prove a simple characterization of its induced congruence, which is given two versions of a complete axiomatization for finite terms. The expressive power of the calculus is demonstrated by giving a straightforward encoding of the strong lazy lambdacalculus, which admits reduction under lambda abstraction.