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Spi Calculus Translated topCalculus Preserving
"... Michael Baldamus, Joachim Parrow, Bj"orn VictorDepartment of Information Technology, Uppsala University, Sweden Abstract We present a concise and natural encoding of the spicalculus into the more basic sscalculus and establish itscorrectness with respect to a formal notion of testing. This is ..."
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Michael Baldamus, Joachim Parrow, Bj"orn VictorDepartment of Information Technology, Uppsala University, Sweden Abstract We present a concise and natural encoding of the spicalculus into the more basic sscalculus and establish itscorrectness with respect to a formal notion of testing
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 222 (4 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...
and their Formal Proofs
, 2012
"... Psicalculi is a parametric framework for extensions of the picalculus, with arbitrary data structures and logical assertions for facts about data. This thesis presents broadcast psicalculi and higherorder psicalculi, two extensions of the psicalculi framework, allowing respectively onetomany ..."
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like to thank my advisor, Joachim Parrow, and my coadvisor, Björn Victor for all their support, help, and advice. I would like to thank all the coauthors; Johannes Borgström, Shuqin Huang,
unknown title
"... The EXPRESS workshops aim at bringing together researchers interested in the relations between various formal systems in computer science, in particular in the field of concurrency. More specifically, they focus on the comparison between programming concepts (such as concurrent, functional, imperati ..."
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in 1997, which took place in Santa Margherita Ligure and was cochaired by Catuscia Palamidessi and Joachim Parrow, was organized as a conference with a call for papers and a significant attendance from outside the project. As of 1998 (so, also this year), the workshops are held as satellite workshops
The polyadic πcalculus: a tutorial
 LOGIC AND ALGEBRA OF SPECIFICATION
, 1991
"... The πcalculus is a model of concurrent computation based upon the notion of naming. It is first presented in its simplest and original form, with the help of several illustrative applications. Then it is generalized from monadic to polyadic form. Semantics is done in terms of both a reduction syste ..."
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Cited by 186 (1 self)
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The πcalculus is a model of concurrent computation based upon the notion of naming. It is first presented in its simplest and original form, with the help of several illustrative applications. Then it is generalized from monadic to polyadic form. Semantics is done in terms of both a reduction system and a version of labelled transitions called commitment; the known algebraic axiomatization of strong bisimilarity isgiven in the new setting, and so also is a characterization in modal logic. Some theorems about the replication operator are proved. Justification for the polyadic form is provided by the concepts of sort and sorting which it supports. Several illustrations of different sortings are given. One example is the presentation of data structures as processes which respect a particular sorting; another is the sorting for a known translation of the λcalculus into πcalculus. For this translation, the equational validity of βconversion is proved with the help of replication theorems. The paper ends with an extension of the πcalculus to ωorder processes, and a brief account of the demonstration by Davide Sangiorgi that higherorder processes maybe faithfully encoded at firstorder. This extends and strengthens the original result of this kind given by Bent Thomsen for secondorder processes.
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 138 (14 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.
Object Ownership and Containment
, 2001
"... Objectoriented programming relies on interobject aliases to implement data structures and other abstractions. Objects have mutable state, but it is when mutable state interacts with aliasing that problems arise. Through aliasing an object's state can be changed without the object being aware ..."
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Cited by 142 (24 self)
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Objectoriented programming relies on interobject aliases to implement data structures and other abstractions. Objects have mutable state, but it is when mutable state interacts with aliasing that problems arise. Through aliasing an object's state can be changed without the object being aware of the changes, potentially violating the object's invariants. This problem is fundamentally unresolvable. Many idioms such as the Observer design pattern rely on it. Hence aliasing cannot be eliminated from objectoriented programming, it can only be managed. Various proposals have appeared in the literature addressing the issue of alias management. The most promising are based on alias encapsulation, which limits access to objects to within certain welldefined boundaries. Our approach called ownership types falls into this category. An object can specify the objects it owns, called its representation, and which objects can access its representation. A type system protects the representation by enforcing a welldefined containment invariant. Our approach is a formal one. Ownership types are cast as a type system using an minor extension to Abadi and Cardelli's object calculus with subtyping. With this formalisation we prove the soundness of our ownership types system and demonstrate that welltyped programs satisfy the containment invariant. In addition, we also provide a firm grounding to enable ownership types to be safely added to an objectoriented programming language with inheritance, subtyping, and nested classes, as well as offering a sound basis for future work. Our type system can model aggregate objects with multiple interface objects sharing representation and friendly functions which access multiple objects' private representations, among other examples, thus over...
A Calculus of Mobile Processes, Part II
, 1989
"... This is the second of two papers in which we present the calculus, a calculus of mobile processes. We provide a detailed presentation of some of the theory of the calculus developed to date, and in particular we establish most of the results stated in the companion paper. 4 Introduction This is ..."
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Cited by 133 (2 self)
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This is the second of two papers in which we present the calculus, a calculus of mobile processes. We provide a detailed presentation of some of the theory of the calculus developed to date, and in particular we establish most of the results stated in the companion paper. 4 Introduction This is the second of two papers in which we present the calculus, a calculus of mobile processes. The companion paper [2] contains an introduction to the calculus through a sequence of examples, together with statements of many results about it. The purpose of the present paper is to provide a detailed presentation of some of the theory of the calculus developed to date, and in particular to establish most of the results stated in the companion paper. Once the motivation and intuition for the calculus are understood, with the help of [2], the present paper serves as a selfcontained development of the theory. To achieve this we have found it necessary to repeat some material from the companion p...
The concurrency workbench: A semantics based tool for the verification of concurrent systems
, 1994
"... The Concurrency Workbench is an automated tool for analyzing networks of finitestate processes expressed in Milner's Calculus of Communicating Systems. Its key feature is its breadth: a variety of different verification methods, including equivalence checking, preorder checking, and model ch ..."
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Cited by 116 (3 self)
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The Concurrency Workbench is an automated tool for analyzing networks of finitestate processes expressed in Milner's Calculus of Communicating Systems. Its key feature is its breadth: a variety of different verification methods, including equivalence checking, preorder checking, and model checking, are supported for several different process semantics. One experience from our work is that a large number of interesting verification methods can be formulated as combinations of a small number of primitive algorithms. The Workbench has been applied to the verification of communications protocols and mutual exclusion algorithms and has proven a valuable aid in teaching and research.
The Update Calculus
, 1997
"... In the update calculus concurrent processes can perform update actions with side effects, and a scoping operator can be used to control the extent of the update. In this way it incorporates fundamental concepts both from imperative languages or concurrent constraints formalisms, and from functional ..."
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Cited by 83 (3 self)
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In the update calculus concurrent processes can perform update actions with side effects, and a scoping operator can be used to control the extent of the update. In this way it incorporates fundamental concepts both from imperative languages or concurrent constraints formalisms, and from functional formalisms such as the  and calculi. Structurally it is similar to but simpler than the calculus; it has only one binding operator and a symmetry between input and output. We define the structured operational semantics and the proper bisimulation equivalence and congruence, and give a complete axiomatization. The calculus turns out to be an asymmetric subcalculus. 1 Introduction Theory of concurrent computation is a diverse field where many different approaches have been proposed and no consensus has emerged on the best paradigms. In this paper we take a step towards unifying two seemingly contradictory schools of thought: global vs local effects of concurrent actions. We define a calc...
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