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84
A Variable Typed Logic of Effects
 Information and Computation
, 1993
"... In this paper we introduce a variable typed logic of effects inspired by the variable type systems of Feferman for purely functional languages. VTLoE (Variable Typed Logic of Effects) is introduced in two stages. The first stage is the firstorder theory of individuals built on assertions of equalit ..."
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Cited by 48 (12 self)
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In this paper we introduce a variable typed logic of effects inspired by the variable type systems of Feferman for purely functional languages. VTLoE (Variable Typed Logic of Effects) is introduced in two stages. The first stage is the firstorder theory of individuals built on assertions of equality (operational equivalence `a la Plotkin), and contextual assertions. The second stage extends the logic to include classes and class membership. The logic we present provides an expressive language for defining and studying properties of programs including program equivalences, in a uniform framework. The logic combines the features and benefits of equational calculi as well as program and specification logics. In addition to the usual firstorder formula constructions, we add contextual assertions. Contextual assertions generalize Hoare's triples in that they can be nested, used as assumptions, and their free variables may be quantified. They are similar in spirit to program modalities in ...
Bisimilarity for a FirstOrder Calculus of Objects with Subtyping
 In Proceedings of the TwentyThird Annual ACM Symposium on Principles of Programming Languages
, 1996
"... Bisimilarity (also known as `applicative bisimulation ') has attracted a good deal of attention as an operational equivalence for calculi. It approximates or even equals Morrisstyle contextual equivalence and admits proofs of program equivalence via coinduction. It has an elementary construc ..."
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Cited by 43 (2 self)
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Bisimilarity (also known as `applicative bisimulation ') has attracted a good deal of attention as an operational equivalence for calculi. It approximates or even equals Morrisstyle contextual equivalence and admits proofs of program equivalence via coinduction. It has an elementary construction from the operational definition of a language. We consider bisimilarity for one of the typed object calculi of Abadi and Cardelli. By defining a labelled transition system for the calculus in the style of Crole and Gordon and using a variation of Howe's method we establish two central results: that bisimilarity is a congruence, and that it equals contextual equivalence. So two objects are bisimilar iff no amount of programming can tell them apart. Our third contribution is to show that bisimilarity soundly models the equational theory of Abadi and Cardelli. This is the first study of contextual equivalence for an object calculus and the first application of Howe's method to subtyping. By the...
From CML to its Process Algebra
 Theoretical Computer Science
"... Reppy's language CML extends Standard ML of Milner et al. with primitives for communication. It thus inherits a notion of strong polymorphic typing and may be equipped with a structural operational semantics. As a first step we formulate an effect system for statically expressing the communicat ..."
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Cited by 36 (6 self)
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Reppy's language CML extends Standard ML of Milner et al. with primitives for communication. It thus inherits a notion of strong polymorphic typing and may be equipped with a structural operational semantics. As a first step we formulate an effect system for statically expressing the communication behaviours of CML programs as these are not reflected in the types. As a second step we adapt the structural operational semantics of CML so as to incorporate behaviours. We then show how types and behaviours evolve in the course of computation: types may decrease and behaviours may lose prefixes as well as decrease. As the syntax of behaviours is rather similar to that of a process algebra our main result may therefore be viewed as regarding the semantics of a process algebra as an abstraction of the semantics of an underlying programming language. This establishes a new kind of connection between "realistic" concurrent programming languages and "theoretical" process algebras. 1 Introduction...
Concurrent ML: Design, Application and Semantics
, 1993
"... Machine" [BB90], except that there are no "cooling" and "heating" transitions (the process sets of this semantics can be thought of as perpetually "hot" solutions). The concurrent evaluation relation extends "7\Gamma!" to finite sets of terms (i.e., proce ..."
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Cited by 34 (0 self)
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Machine" [BB90], except that there are no "cooling" and "heating" transitions (the process sets of this semantics can be thought of as perpetually "hot" solutions). The concurrent evaluation relation extends "7\Gamma!" to finite sets of terms (i.e., processes) and adds additional rules for process creation, channel creation, and communication. We assume a set of process identifiers, and define the set of processes and process sets as: ß 2 ProcId process IDs p = hß; ei 2 Proc = (ProcId \Theta Exp) processes P 2 Fin(Proc) process sets We often write a process as hß; E[e]i, where the evaluation context serves the role of the program counter, marking the current state of evaluation. Definition4. A process set P is wellformed if for all hß; ei 2 P the following hold:  FV(e) = ; (e is closed), and  there is no e 0 6= e, such that hß; e 0 i 2 P. It is occasionally useful to view wellformed process sets as finite maps from ProcId to Exp. If P is a finite set of process state...
Operational congruences for reactive systems
, 2001
"... This document consists of a slightly revised and corrected version of a dissertation ..."
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Cited by 34 (4 self)
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This document consists of a slightly revised and corrected version of a dissertation
A Syntactic Theory of Dynamic Binding
 HigherOrder and Symbolic Computation
, 1997
"... . Dynamic binding, which has always been associated with Lisp, is still semantically obscure to many. Although largely replaced by lexical scoping, not only does dynamic binding remain an interesting and expressive programming technique in specialised circumstances, but also it is a key notion in se ..."
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Cited by 33 (1 self)
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. Dynamic binding, which has always been associated with Lisp, is still semantically obscure to many. Although largely replaced by lexical scoping, not only does dynamic binding remain an interesting and expressive programming technique in specialised circumstances, but also it is a key notion in semantics. This paper presents a syntactic theory that enables the programmer to perform equational reasoning on programs using dynamic binding. The theory is proved to be sound and complete with respect to derivations allowed on programs in "dynamicenvironment passing style". From this theory, we derive a sequential evaluation function in a contextrewriting system. Then, we exhibit the power and usefulness of dynamic binding in two different ways. First, we prove that dynamic binding adds expressiveness to a purely functional language. Second, we show that dynamic binding is an essential notion in semantics that can be used to define the semantics of exceptions. Afterwards, we further refin...
Compilation and Equivalence of Imperative Objects
, 1998
"... We adopt the untyped imperative object calculus of Abadi and Cardelli as a minimal setting in which to study problems of compilation and program equivalence that arise when compiling objectoriented languages. We present both a bigstep and a smallstep substitutionbased operational semantics fo ..."
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Cited by 32 (4 self)
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We adopt the untyped imperative object calculus of Abadi and Cardelli as a minimal setting in which to study problems of compilation and program equivalence that arise when compiling objectoriented languages. We present both a bigstep and a smallstep substitutionbased operational semantics for the calculus. Our rst two results are theorems asserting the equivalence of our substitutionbased semantics with a closurebased semantics like that given by Abadi and Cardelli. Our third result is a direct proof of the correctness of compilation to a stackbased abstract machine via a smallstep decompilation algorithm. Our fourth result is that contextual equivalence of objects coincides with a form of Mason and Talcott's CIU equivalence; the latter provides a tractable means of establishing operational equivalences. Finally, we prove correct an algorithm, used in our prototype compiler, for statically resolving method osets. This is the rst study of correctness of an objectoriented abstract machine, and of operational equivalence for the imperative object calculus.
Polymorphism by name for references and continuations
 IN CONFERENCE RECORD OF THE TWENTIETH ANNUAL ACM SYMPOSIUM ON PRINCIPLES OF PROGRAMMING LANGUAGES
, 1993
"... This article investigates an MLlike language with byname semantics for polymorphism: polymorphic objects are not evaluated once for all at generalization time, but reevaluated at each specialization. Unlike the standard ML semantics, the byname semantics works well with polymorphic references and ..."
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Cited by 31 (1 self)
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This article investigates an MLlike language with byname semantics for polymorphism: polymorphic objects are not evaluated once for all at generalization time, but reevaluated at each specialization. Unlike the standard ML semantics, the byname semantics works well with polymorphic references and polymorphic continuations: the naive typing rules for references and for continuations are sound with respect to this semantics. Polymorphism by name leads to a better integration of these imperative features into the ML type discipline. Practical experience shows that it retains most of the eciency and predictability of polymorphism by value.
Foundations of Modular SOS
, 1999
"... A novel form of labelled transition system is proposed, where the labels are the arrows of a category, and adjacent labels in computations are required to be composable. Such transition systems provide the foundations for modular SOS descriptions of programming languages. Three ..."
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Cited by 29 (6 self)
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A novel form of labelled transition system is proposed, where the labels are the arrows of a category, and adjacent labels in computations are required to be composable. Such transition systems provide the foundations for modular SOS descriptions of programming languages. Three