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Ownership Transfer and Abstraction
, 2003
"... Ownership confinement expresses encapsulation in heap structures, in support of modular reasoning about e#ects, representation independence, and other properties. This paper studies heap encapsulation from the perspective of substitutability for the class construct of Javalike languages and a p ..."
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Ownership confinement expresses encapsulation in heap structures, in support of modular reasoning about e#ects, representation independence, and other properties. This paper studies heap encapsulation from the perspective of substitutability for the class construct of Javalike languages and a particular form of confinement is justified by a representation independence result. A syntaxdirected static analysis is specified and proved sound for checking confinement in the presence of ownership transfer.
A Simple Adequate Categorical Model for PCF
 In Proceedings of Third International Conference on Typed Lambda Calculi and Applications
, 1997
"... Usually types of PCF are interpreted as cpos and terms as continuous functions. It is then the case that nontermination of a closed term of ground type corresponds to the interpretation being bottom; we say that the semantics is adequate. We shall here present an axiomatic approach to adequacy for ..."
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Cited by 4 (0 self)
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Usually types of PCF are interpreted as cpos and terms as continuous functions. It is then the case that nontermination of a closed term of ground type corresponds to the interpretation being bottom; we say that the semantics is adequate. We shall here present an axiomatic approach to adequacy for PCF in the sense that we will introduce categorical axioms enabling an adequate semantics to be given. We assume the presence of certain "bottom" maps with the role of being the interpretation of nonterminating terms, but the orderstructure is left out. This is different from previous approaches where some kind of ordertheoretic structure has been considered as part of an adequate categorical model for PCF. We take the point of view that partiality is the fundamental notion from which orderstructure should be derived, which is corroborated by the observation that our categorical model induces an ordertheoretic model for PCF in a canonical way.
Blaming the Client: On Data Refinement in the Presence of Pointers
 TO APPEAR IN FORMAL ASPECTS OF COMPUTING
"... Data refinement is a common approach to reasoning about programs, based on establishing that a concrete program indeed satisfies all the required properties imposed by an intended abstract pattern. Reasoning about programs in this setting becomes complex when use of pointers is assumed and, moreove ..."
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Data refinement is a common approach to reasoning about programs, based on establishing that a concrete program indeed satisfies all the required properties imposed by an intended abstract pattern. Reasoning about programs in this setting becomes complex when use of pointers is assumed and, moreover, a wellknown method for proving data refinement, namely the forward simulation method, becomes unsound in presence of pointers. The reason for unsoundness is the failure of the “lifting theorem” for simulations: that a simulation between abstract and concrete modules can be lifted to all client programs. The result is that simulation does not imply that a concrete can replace an abstract module in all contexts. Our diagnosis of this problem is that unsoundness is due to interference from the client programs. Rather than blame a module for the unsoundness of lifting simulations, our analysis places the blame on the client programs which cause the interference: when interference is not present, soundness is recovered. Technically, we present a novel instrumented semantics which is capable of detecting interference between a module and its client. With use of special simulation relations, namely growing relations, and interpreting the simulation method using the instrumented semantics, we obtain a lifting theorem. We then show situations under which simulation does indeed imply refinement.
Theory for Software Verification
, 2009
"... Semantic models are the basis for specification and verification of software. Operational, denotational, and axiomatic or algebraic methods offer complementary insights and reasoning techniques which are surveyed here. Unifying theories are needed to link models. Also considered are selected program ..."
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Semantic models are the basis for specification and verification of software. Operational, denotational, and axiomatic or algebraic methods offer complementary insights and reasoning techniques which are surveyed here. Unifying theories are needed to link models. Also considered are selected programming features for which new models are needed.
βηcomplete models for System F
, 2000
"... We show that Friedman's proof of the existence of nontrivial βηcomplete models of λ→ can be extended to system F. We isolate a set of conditions which are sufficient to ensure βηcompleteness for a model of F (and αcompleteness at the level of types), and we di ..."
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We show that Friedman's proof of the existence of nontrivial βηcomplete models of λ→ can be extended to system F. We isolate a set of conditions which are sufficient to ensure βηcompleteness for a model of F (and αcompleteness at the level of types), and we discuss which class of models we get. In particular, the model introduced in [5], having as polymorphic maps exactly all possible Scott continuous maps, is βηcomplete and is hence the first known complete nonsyntactic model of F. In order to have a suitable framework where to express the conditions and develop the proof, we also introduce the very natural notion of "polymax models" of System F. 1
unknown title
, 905
"... An arithmetical proof of the strong normalization for the λcalculus with recursive equations on types ..."
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An arithmetical proof of the strong normalization for the λcalculus with recursive equations on types