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Linearity, Sharing and State: a fully abstract game semantics for Idealized Algol with active expressions
 ALGOLLIKE LANGUAGES
, 1997
"... The manipulation of objects with state which changes over time is allpervasive in computing. Perhaps the simplest example of such objects are the program variables of classical imperative languages. An important strand of work within the study of such languages, pioneered by John Reynolds, focusses ..."
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The manipulation of objects with state which changes over time is allpervasive in computing. Perhaps the simplest example of such objects are the program variables of classical imperative languages. An important strand of work within the study of such languages, pioneered by John Reynolds, focusses on "Idealized Algol", an elegant synthesis of imperative and functional features. We present a novel semantics for Idealized Algol using games, which is quite unlike traditional denotational models of state. The model takes into account the irreversibility of changes in state, and makes explicit the difference between copying and sharing of entities. As a formal measure of the accuracy of our model, we obtain a full abstraction theorem for Idealized Algol with active expressions.
Retracing some paths in Process Algebra
"... Introduction 2 The semantic universe: transducers Similar ideas appeared independently in the work of Hans Bekic [Bek71]. Samson Abramsky Laboratory for the Foundations of Computer Science University of Edinburgh The very existence of the conference bears witness to the fact that "concurrency ..."
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Introduction 2 The semantic universe: transducers Similar ideas appeared independently in the work of Hans Bekic [Bek71]. Samson Abramsky Laboratory for the Foundations of Computer Science University of Edinburgh The very existence of the conference bears witness to the fact that "concurrency theory" has developed into a subject unto itself, with substantially di#erent emphases and techniques to those prominent elsewhere in the semantics of computation. Whatever the past merits of this separate development, it seems timely to look for some convergence and unification. In addressing these issues, I have found it instructive to trace some of the received ideas in concurrency back to their origins in the early 1970's. In particular, I want to focus on a seminal paper by Robin Milner [Mil75] , which led in a fairly direct line to his enormously influential work on [Mil80, Mil89]. I will take (to the extreme) the liberty of of applying hindsight, and show how some di
CallbyValue Games
, 1997
"... . A general construction of models of callbyvalue from models of callbyname computation is described. The construction makes essential use of the properties of sum types in common denotational models of callbyname. When applied to categories of games, it yields fully abstract models of the cal ..."
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. A general construction of models of callbyvalue from models of callbyname computation is described. The construction makes essential use of the properties of sum types in common denotational models of callbyname. When applied to categories of games, it yields fully abstract models of the callbyvalue functional language PCFv , which can be extended to incorporate recursive types, and of a language with local references as in Standard ML. 1 Introduction In recent years game semantics has emerged as a novel and intuitively appealing approach to modelling programming languages. Its first success was in providing a syntaxfree description of a fully abstract model of PCF [10, 1, 15]; full abstraction results have also been obtained for untyped and recursively typed functional languages, as well as languages with imperative features [12, 3]. However, none of this work addressed the problem of modelling callbyvalue languagesa major shortcoming, given that many reallife langua...
Models of Sharing Graphs: A Categorical Semantics of let and letrec
, 1997
"... To my parents A general abstract theory for computation involving shared resources is presented. We develop the models of sharing graphs, also known as term graphs, in terms of both syntax and semantics. According to the complexity of the permitted form of sharing, we consider four situations of sha ..."
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To my parents A general abstract theory for computation involving shared resources is presented. We develop the models of sharing graphs, also known as term graphs, in terms of both syntax and semantics. According to the complexity of the permitted form of sharing, we consider four situations of sharing graphs. The simplest is firstorder acyclic sharing graphs represented by letsyntax, and others are extensions with higherorder constructs (lambda calculi) and/or cyclic sharing (recursive letrec binding). For each of four settings, we provide the equational theory for representing the sharing graphs, and identify the class of categorical models which are shown to be sound and complete for the theory. The emphasis is put on the algebraic nature of sharing graphs, which leads us to the semantic account of them. We describe the models in terms of the notions of symmetric monoidal categories and functors, additionally with symmetric monoidal adjunctions and traced
Algorithmic Game Semantics
 In Schichtenberg and Steinbruggen [16
, 2001
"... Introduction SAMSON ABRAMSKY (samson@comlab.ox.ac.uk) Oxford University Computing Laboratory 1. Introduction Game Semantics has emerged as a powerful paradigm for giving semantics to a variety of programming languages and logical systems. It has been used to construct the first syntaxindependen ..."
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Cited by 54 (3 self)
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Introduction SAMSON ABRAMSKY (samson@comlab.ox.ac.uk) Oxford University Computing Laboratory 1. Introduction Game Semantics has emerged as a powerful paradigm for giving semantics to a variety of programming languages and logical systems. It has been used to construct the first syntaxindependent fully abstract models for a spectrum of programming languages ranging from purely functional languages to languages with nonfunctional features such as control operators and locallyscoped references [4, 21, 5, 19, 2, 22, 17, 11]. A substantial survey of the state of the art of Game Semantics circa 1997 was given in a previous Marktoberdorf volume [6]. Our aim in this tutorial presentation is to give a first indication of how Game Semantics can be developed in a new, algorithmic direction, with a view to applications in computerassisted verification and program analysis. Some promising steps have already been taken in this
Full Abstraction for Idealized Algol with Passive Expressions
, 1998
"... ion for Idealized Algol with Passive Expressions Samson Abramsky University of Edinburgh Department of Computer Science James Clerk Maxwell Building Edinburgh EH9 3JZ Scotland samson@dcs.ed.ac.uk Guy McCusker St John's College Oxford OX1 3JP, England mccusker@comlab.ox.ac.uk Abstract A ful ..."
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ion for Idealized Algol with Passive Expressions Samson Abramsky University of Edinburgh Department of Computer Science James Clerk Maxwell Building Edinburgh EH9 3JZ Scotland samson@dcs.ed.ac.uk Guy McCusker St John's College Oxford OX1 3JP, England mccusker@comlab.ox.ac.uk Abstract A fully abstract games model of Reynolds' Idealized Algol is described. The model gives a semantic account of the distinction between active types, such as commands, which admit sideeffecting behaviour, and passive types, such as expressions, which do not. Keywords: Algollike languages, game semantics, full abstraction. 1 Introduction Our aim in this paper is to give the first syntaxindependent construction of a fully abstract model for Idealized Algol. John Reynolds proposed Idealized Algol as capturing the essence of Algol 60 [32]; it is an elegant synthesis of the features of a simple blockstructured imperative programming language with those of higherorder functional programming. As such it...
A Semantic analysis of control
, 1998
"... This thesis examines the use of denotational semantics to reason about control flow in sequential, basically functional languages. It extends recent work in game semantics, in which programs are interpreted as strategies for computation by interaction with an environment. Abramsky has suggested that ..."
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This thesis examines the use of denotational semantics to reason about control flow in sequential, basically functional languages. It extends recent work in game semantics, in which programs are interpreted as strategies for computation by interaction with an environment. Abramsky has suggested that an intensional hierarchy of computational features such as state, and their fully abstract models, can be captured as violations of the constraints on strategies in the basic functional model. Nonlocal control flow is shown to fit into this framework as the violation of strong and weak ‘bracketing ’ conditions, related to linear behaviour. The language µPCF (Parigot’s λµ with constants and recursion) is adopted as a simple basis for highertype, sequential computation with access to the flow of control. A simple operational semantics for both callbyname and callbyvalue evaluation is described. It is shown that dropping the bracketing condition on games models of PCF yields fully abstract models of µPCF.
Games in the Semantics of Programming Languages
 Dept. of Philosophy, University of Amsterdam
, 1997
"... ion for PCF Motivated by the full completeness results, it became of compelling interest to reexamine perhaps the bestknown "open problem" in the semantics of programming languages, namely the "Full Abstraction problem for PCF", using the new tools provided by game semantics. ..."
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ion for PCF Motivated by the full completeness results, it became of compelling interest to reexamine perhaps the bestknown "open problem" in the semantics of programming languages, namely the "Full Abstraction problem for PCF", using the new tools provided by game semantics. 2 PCF is a higherorder functional programming language; modulo issues of the parameterpassing strategies, it forms a fragment of any programming language with higherorder procedures (which includes any reasonably expressive objectoriented language). The aspect of the Full Abstraction problem I personally found most interesting was: to construct a syntaxindependent model in which every element is the denotation of some program (note the analogy with full completeness, whose definition had in turn been motivated in part by this aspect of full abstraction). This is not how the problem was originally formulated, but by "general abstract nonsense", given such a model one can always quotient it to get a fully ab...
Fully Complete Models for ML Polymorphic Types
, 1999
"... We present an axiomatic characterization of models fullycomplete for MLpolymorphic types of system F. This axiomatization is given for hyperdoctrine models, which arise as adjoint models, i.e. coKleisli categories of suitable linear categories. Examples of adjoint models can be obtained from cate ..."
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We present an axiomatic characterization of models fullycomplete for MLpolymorphic types of system F. This axiomatization is given for hyperdoctrine models, which arise as adjoint models, i.e. coKleisli categories of suitable linear categories. Examples of adjoint models can be obtained from categories of Partial Equivalence Relations over Linear Combinatory Algebras. We show that a special linear combinatory algebra of partial involutions induces an hyperdoctrine which satisfies our axiomatization, and hence it provides a fullycomplete model for MLtypes.
A Game Semantics of Linearly Used Continuations
 FoSSaCs’03, LNCS 2620, 313–327
, 2002
"... We present an analysis of the \linearly used continuationpassing interpretation" of functional languages, based on game semantics. ..."
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We present an analysis of the \linearly used continuationpassing interpretation" of functional languages, based on game semantics.