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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.
Constructive Data Refinement in Typed Lambda Calculus
, 2000
"... . A new treatment of data refinement in typed lambda calculus is proposed, based on prelogical relations [HS99] rather than logical relations as in [Ten94], and incorporating a constructive element. Constructive data refinement is shown to have desirable properties, and a substantial example of ..."
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. A new treatment of data refinement in typed lambda calculus is proposed, based on prelogical relations [HS99] rather than logical relations as in [Ten94], and incorporating a constructive element. Constructive data refinement is shown to have desirable properties, and a substantial example of refinement is presented. 1 Introduction Various treatments of data refinement in the context of typed lambda calculus, beginning with Tennent's in [Ten94], have used logical relations to formalize the intuitive notion of refinement. This work has its roots in [Hoa72], which proposes that the correctness of a concrete version of an abstract program be verified using an invariant on the domain of concrete values together with a function mapping concrete values (that satisfy the invariant) to abstract values. In algebraic terms, what is required is a homomorphism from a subalgebra of the concrete algebra to the abstract algebra. A strictly more general method is to take a homomorphic relatio...
A game semantics of Idealized CSP
 Seventeenth Conference on Mathematical Foundations of Programming Semantics, MFPS ’01, volume 45 of Electronic notes in Theoretical Computer Science
, 2001
"... A games semantics is described for a typed functional language which includes primitives for parallel composition and for synchronous communication on private channels. The semantics is based on a category obtained by extending "HylandOng games" with a representation of multiple threads o ..."
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A games semantics is described for a typed functional language which includes primitives for parallel composition and for synchronous communication on private channels. The semantics is based on a category obtained by extending "HylandOng games" with a representation of multiple threads of control using "concurrency pointers" which express a new kind of causality relation between moves. The semantics is proved to be fully abstract for "channelfree" types with respect to a mayandmust equivalence for the finitary fragment, and with respect to mayequivalence for the whole language, using factorization results to reduce definability to the sequential case.
Games and Sequential Algorithms
, 2001
"... The relationship between HylandOngstyle games and BerryCurien sequential algorithms is investigated, with the object of describing semantic solutions to two problems  to characterise eectively the \minimal models" of the simplytyped calculus and the fully abstract model of PCF with co ..."
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The relationship between HylandOngstyle games and BerryCurien sequential algorithms is investigated, with the object of describing semantic solutions to two problems  to characterise eectively the \minimal models" of the simplytyped calculus and the fully abstract model of PCF with control operators  which are shown to be equivalent.
Matching typed and untyped realizability (Extended abstract)
"... Realizability interpretations of logics are given by saying what it means for computational objects of some kind to realize logical formulae. The computational objects in question might be drawn from an untyped universe of computation, such as a partial combinatory algebra, or they might be typed ob ..."
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Realizability interpretations of logics are given by saying what it means for computational objects of some kind to realize logical formulae. The computational objects in question might be drawn from an untyped universe of computation, such as a partial combinatory algebra, or they might be typed objects such as terms of a PCFstyle programming language. In some instances, one can show that a particular untyped realizability interpretation matches a particular typed one, in the sense that they give the same set of realizable formulae. In this case, we have a very good fit indeed between the typed language and the untyped realizability model—we refer to this condition as (constructive) logical full abstraction. We give some examples of this situation for a variety of extensions of PCF. Of particular interest are some models that are logically fully abstract for typed languages including nonfunctional features. Our results establish connections between what is computable in various programming languages, and what is true inside various realizability toposes. We consider some examples of logical formulae to illustrate these ideas, in particular their application to exact realnumber computability. The present article summarizes the material I presented at the Domains IV workshop, plus a few subsequent developments; it is really an extended abstract for a projected journal paper. No proofs are included in the present version. 0
Fully Abstract Bidomain Models of the λCalculus
, 2001
"... We present a proof that the canonical models of the untyped λcalculus  with callbyvalue and lazy callbyname evaluation  in the category of bidomains and continuous and stable functions are fully abstract. This is achieved by showing that bidomains yield a fully abstract model of a versio ..."
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We present a proof that the canonical models of the untyped λcalculus  with callbyvalue and lazy callbyname evaluation  in the category of bidomains and continuous and stable functions are fully abstract. This is achieved by showing that bidomains yield a fully abstract model of a version of Plotkin's FPC in which the constructor for sum types is restricted to its unary form  lifting. It is shown that full abstraction for this model can be reduced to denability for the fragment corresponding to "unary PCF". An algorithm devised by SchmidtSchau is used to show that the bidomain model of this fragment is fully abstract.