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Pict: A programming language based on the picalculus
 PROOF, LANGUAGE AND INTERACTION: ESSAYS IN HONOUR OF ROBIN MILNER
, 1997
"... The πcalculus offers an attractive basis for concurrent programming. It is small, elegant, and well studied, and supports (via simple encodings) a wide range of highlevel constructs including data structures, higherorder functional programming, concurrent control structures, and objects. Moreover ..."
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Cited by 254 (8 self)
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The πcalculus offers an attractive basis for concurrent programming. It is small, elegant, and well studied, and supports (via simple encodings) a wide range of highlevel constructs including data structures, higherorder functional programming, concurrent control structures, and objects. Moreover, familiar type systems for the calculus have direct counterparts in the πcalculus, yielding strong, static typing for a highlevel language using the πcalculus as its core. This paper describes Pict, a stronglytyped concurrent programming language constructed in terms of an explicitlytypedcalculus core language.
A Foundation for Actor Computation
 Journal of Functional Programming
, 1998
"... We present an actor language which is an extension of a simple functional language, and provide a precise operational semantics for this extension. Actor configurations represent open distributed systems, by which we mean that the specification of an actor system explicitly takes into account the in ..."
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Cited by 222 (51 self)
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We present an actor language which is an extension of a simple functional language, and provide a precise operational semantics for this extension. Actor configurations represent open distributed systems, by which we mean that the specification of an actor system explicitly takes into account the interface with external components. We study the composability of such systems. We define and study various notions of testing equivalence on actor expressions and configurations. The model we develop provides fairness. An important result is that the three forms of equivalence, namely, convex, must, and may equivalences, collapse to two in the presence of fairness. We further develop methods for proving laws of equivalence and provide example proofs to illustrate our methodology.
Predicting the Drape of Woven Cloth Using Interacting Particles
, 1994
"... We demonstrate a physicallybased technique for predicting the drape of a wide variety of woven fabrics. The approach exploits a theoretical model that explicitly represents the microstructure of woven cloth with interacting particles, rather than utilizing a continuum approximation. By testing a cl ..."
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Cited by 121 (5 self)
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We demonstrate a physicallybased technique for predicting the drape of a wide variety of woven fabrics. The approach exploits a theoretical model that explicitly represents the microstructure of woven cloth with interacting particles, rather than utilizing a continuum approximation. By testing a cloth sample in a Kawabata fabric testing device, we obtain data that is used to tune the model's energy functions, so that it reproduces the draping behavior of the original material. Photographs, comparing the drape of actual cloth with visualizations of simulation results, show that we are able to reliably model the unique largescale draping characteristics of distinctly different fabric types. iii Figure 1.1: Draping cloth objects 1 Introduction The vast number of uses for cloth are mirrored in the extraordinary variety of types of woven fabrics. These range from the most exquisite fine silks, to the coarsest of burlaps, and are woven from such diverse fibers as natural wool and synth...
Decoding Choice Encodings
, 1999
"... We study two encodings of the asynchronous #calculus with inputguarded choice into its choicefree fragment. One encoding is divergencefree, but refines the atomic commitment of choice into gradual commitment. The other preserves atomicity, but introduces divergence. The divergent encoding is ..."
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Cited by 97 (5 self)
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We study two encodings of the asynchronous #calculus with inputguarded choice into its choicefree fragment. One encoding is divergencefree, but refines the atomic commitment of choice into gradual commitment. The other preserves atomicity, but introduces divergence. The divergent encoding is fully abstract with respect to weak bisimulation, but the more natural divergencefree encoding is not. Instead, we show that it is fully abstract with respect to coupled simulation, a slightly coarserbut still coinductively definedequivalence that does not enforce bisimilarity of internal branching decisions. The correctness proofs for the two choice encodings introduce a novel proof technique exploiting the properties of explicit decodings from translations to source terms.
The Polymorphic Picalculus: Theory and Implementation
, 1995
"... We investigate whether the πcalculus is able to serve as a good foundation for the design and implementation of a stronglytyped concurrent programming language. The first half of the dissertation examines whether the πcalculus supports a simple type system which is flexible enough to provide a su ..."
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Cited by 95 (0 self)
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We investigate whether the πcalculus is able to serve as a good foundation for the design and implementation of a stronglytyped concurrent programming language. The first half of the dissertation examines whether the πcalculus supports a simple type system which is flexible enough to provide a suitable foundation for the type system of a concurrent programming language. The second half of the dissertation considers how to implement the πcalculus efficiently, starting with an abstract machine for πcalculus and finally presenting a compilation of πcalculus to C. We start the dissertation by presenting a simple, structural type system for πcalculus, and then, after proving the soundness of our type system, show how to infer principal types for πterms. This simple type system can be extended to include useful typetheoretic constructions such as recursive types and higherorder polymorphism. Higherorder polymorphism is important, since it gives us the ability to implement abstract datatypes in a typesafe manner, thereby providing a greater degree of modularity for πcalculus programs. The functional computational paradigm plays an important part in many programming languages. It is wellknown that the πcalculus can encode functional computation. We go further and show that the type structure of λterms is preserved by such encodings, in the sense that we can relate the type of a λterm to the type of its encoding in the πcalculus. This means that a πcalculus programming language can genuinely support typed functional programming as a special case. An efficient implementation of πcalculus is necessary if we wish to consider πcalculus as an operational foundation for concurrent programming. We first give a simple abstract machine for πcalculus and prove it correct. We then show how this abstract machine inspires a simple, but efficient, compilation of πcalculus to C (which now forms the basis of the Pict programming language implementation).
Localities and Failures
 In Proc. 14th Foundations of Software Technology and Theoretical Computer Science
, 1995
"... We present a simple extension of the ßcalculus with located actions and channels and with location names as firstclass data, which models the notion of locality and failure present in the higherorder, distributed programming language Facile. The interaction between localities and failures disting ..."
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Cited by 56 (0 self)
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We present a simple extension of the ßcalculus with located actions and channels and with location names as firstclass data, which models the notion of locality and failure present in the higherorder, distributed programming language Facile. The interaction between localities and failures distinguishes our approach from previous ones where the notion of locality is considered in isolation. We argue that the combination of these two features leads, at least from the distributed programming viewpoint, to a more natural semantics. We then discuss the translation of this calculus into a standard simplysorted ßcalculus and show its adequacy with respect to a barbed bisimulation based semantics. In the translation each location is represented by a special process which interacts, by means of a simple protocol, with any process of the original program that wants to access resources depending on that location. We also employ our translation in the verification of a very simple faulttoler...
A Fully Abstract Semantics for a Concurrent Functional Language With Monadic Types
, 1995
"... This paper presents a typed higherorder concurrent functional programming language, based on Moggi's monadic metalanguage and Reppy's Concurrent ML. We present an operational semantics for the language, and show that a higherorder variant of the traces model is fully abstract for maytesting. This p ..."
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Cited by 21 (4 self)
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This paper presents a typed higherorder concurrent functional programming language, based on Moggi's monadic metalanguage and Reppy's Concurrent ML. We present an operational semantics for the language, and show that a higherorder variant of the traces model is fully abstract for maytesting. This proof uses a program logic based on HennessyMilner logic and Abramsky's domain theory in logical form.
Actor Languages: Their Syntax, Semantics, Translation, and Equivalence
 Theoretical Computer Science
, 1999
"... In this paper we present two actor languages and a semantics preserving translation between them. The source of the translation is a highlevel language that provides objectbased programming abstractions. The target is a simple functional language extended with basic primitives for actor computatio ..."
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Cited by 12 (6 self)
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In this paper we present two actor languages and a semantics preserving translation between them. The source of the translation is a highlevel language that provides objectbased programming abstractions. The target is a simple functional language extended with basic primitives for actor computation. The semantics preserved is the interaction semantics of actor systemssets of possible interactions of a system with its environment. The proof itself is of interest since it demonstrates a methodology based on the actor theory framework for reasoning about correctness of transformations and translations of actor programs and languages and more generally of concurrent object languages.
Compiler Correctness for Parallel Languages
, 1994
"... We present a paradigm for proving the correctness of compilers for languages with parallelism. The source language is given a denotational semantics as a compositional translation to a higherorder process calculus. The target language is also given a denotational semantics as a compositional transl ..."
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Cited by 11 (2 self)
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We present a paradigm for proving the correctness of compilers for languages with parallelism. The source language is given a denotational semantics as a compositional translation to a higherorder process calculus. The target language is also given a denotational semantics as a compositional translation to the same process calculus. We show the compiler is correct in that it preserves denotation up to bisimulation. The target language is also given an operational semantics, and this operational semantics is shown correct in the sense that it is branchingbisimilar to the denotational semantics of the target language. Together, these results show that for any program, the operational semantics of the target code is branchingbisimilar to the semantics of the source code. 1 Introduction In a series of papers in the early 80's [35, 34, 36, 12] we proposed a paradigm for semanticsbased compiler correctness, and over the last several years we have begun putting this paradigm into practic...
Full Abstractness for a Functional/Concurrent Language With HigherOrder ValuePassing
, 1998
"... We study an applied typed callbyvalue calculus which in addition to the usual types for higherorder functions contains an extra type called proc, for processes. The constructors for terms of this type are similar to those found in standard process calculi such as CCS. We first give an operationa ..."
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Cited by 6 (2 self)
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We study an applied typed callbyvalue calculus which in addition to the usual types for higherorder functions contains an extra type called proc, for processes. The constructors for terms of this type are similar to those found in standard process calculi such as CCS. We first give an operational semantics for this language in terms of a labelled transition system which is then used to give a behavioural preorder based on contexts: the expression N dominates M if in every appropriate context if M can produce a boolean value then so can N. Based on standard domain constructors we define a model, a prime algebraic lattice, which is fully abstract with respect to this behaviour preorder.