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A Concurrent Object Calculus: Reduction and Typing
 HLCL'98 TO APPEAR
, 1998
"... We obtain a new formalism for concurrent objectoriented languages by extending Abadi and Cardelli's imperative object calculus with operators for concurrency from thecalculus and with operators for synchronisation based on mutexes. Our syntax of terms is extremely expressive; in a precise sense it ..."
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Cited by 79 (4 self)
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We obtain a new formalism for concurrent objectoriented languages by extending Abadi and Cardelli's imperative object calculus with operators for concurrency from thecalculus and with operators for synchronisation based on mutexes. Our syntax of terms is extremely expressive; in a precise sense it unifies notions of expression, process, store, thread, and configuration. We present a chemicalstyle reduction semantics, and prove it equivalent to a structural operational semantics. We identify a deterministic fragment that is closed under reduction and show that it includes the imperative object calculus. A collection of type systems for objectoriented constructs is at the heart of Abadi and Cardelli's work. We recast one of Abadi and Cardelli's firstorder type systems with object types and subtyping in the setting of our calculus and prove subject reduction. Since our syntax of terms includes both stores and running expressions, we avoid the need to separate store typing from typing of expressions. We translate asynchronous communication channels and the choicefree asynchronouscalculus into our calculus to illustrate its expressiveness; the types of readonly and writeonly channels are supertypes of readwrite channels.
A calculus of mobile resources
, 2002
"... We introduce a calculus of Mobile Resources (MR) tailored for the design and analysis of systems containing mobile, possibly nested, computing devices that may have resource and access constraints, and which are not copyable nor modifiable per se. We provide a reduction as well as a labelled tran ..."
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Cited by 39 (11 self)
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We introduce a calculus of Mobile Resources (MR) tailored for the design and analysis of systems containing mobile, possibly nested, computing devices that may have resource and access constraints, and which are not copyable nor modifiable per se. We provide a reduction as well as a labelled transition semantics and prove a correspondence between barbed bisimulation congruence and a higherorder bisimulation. We provide examples of the expressiveness of the calculus, and apply the theory to prove one of its characteristic properties. This report is the full version of [11].
A fully abstract may testing semantics for concurrent objects
 In Proceedings of LICS ’02. IEEE, Computer
, 2002
"... This paper provides a fully abstract semantics for a variant of the concurrent object calculus. We define may testing for concurrent object components and then characterise it using a trace semantics inspired by UML interaction diagrams. The main result of this paper is to show that the trace semant ..."
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Cited by 38 (4 self)
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This paper provides a fully abstract semantics for a variant of the concurrent object calculus. We define may testing for concurrent object components and then characterise it using a trace semantics inspired by UML interaction diagrams. The main result of this paper is to show that the trace semantics is fully abstract for may testing. This is the first such result for a concurrent object language. 1.
A Congruence Theorem for Structured Operational Semantics of HigherOrder Languages
, 1997
"... In this paper we describe the promoted tyft/tyxt rule format for defining higherorder languages. The rule format is a generalization of Groote and Vaandrager 's tyft/tyxt format in which terms are allowed as labels on transitions in rules. We prove that bisimulation is a congruence for any languag ..."
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Cited by 36 (0 self)
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In this paper we describe the promoted tyft/tyxt rule format for defining higherorder languages. The rule format is a generalization of Groote and Vaandrager 's tyft/tyxt format in which terms are allowed as labels on transitions in rules. We prove that bisimulation is a congruence for any language defined in promoted tyft/tyxt format and demonstrate the usefulness of the rule format by presenting promoted tyft/tyxt definitions for the lazy calculus, CHOCS and the ßcalculus. 1 Introduction For a programming language definition that uses bisimulation as the notion of equivalence, it is desirable for the bisimulation relation to be compatible with the language constructs; i.e. that bisimulation be a congruence. Several rule formats have been defined, so that as long as a definition satisfies certain syntactic constraints, then the defined bisimulation relation is guaranteed to be a congruence. However these rule formats have not been widely used for defining languages with higher...
Environmental bisimulations for higherorder languages
 In TwentySecond Annual IEEE Symposium on Logic in Computer Science
, 2007
"... Developing a theory of bisimulation in higherorder languages can be hard. Particularly challenging can be: (1) the proof of congruence, as well as enhancements of the bisimulation proof method with “upto context ” techniques, and (2) obtaining definitions and results that scale to languages with d ..."
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Cited by 35 (10 self)
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Developing a theory of bisimulation in higherorder languages can be hard. Particularly challenging can be: (1) the proof of congruence, as well as enhancements of the bisimulation proof method with “upto context ” techniques, and (2) obtaining definitions and results that scale to languages with different features. To meet these challenges, we present environmental bisimulations, a form of bisimulation for higherorder languages, and its basic theory. We consider four representative calculi: pure λcalculi (callbyname and callbyvalue), callbyvalue λcalculus with higherorder store, and then HigherOrder πcalculus. In each case: we present the basic properties of environmental bisimilarity, including congruence; we show that it coincides with contextual equivalence; we develop some upto techniques, including upto context, as examples of possible enhancements of the associated bisimulation method. Unlike previous approaches (such as applicative bisimulations, logical relations, SumiiPierceKoutavasWand), our method does not require induction/indices on evaluation derivation/steps (which may complicate the proofs of congruence, transitivity, and the combination with upto techniques), or sophisticated methods such as Howe’s for proving congruence. It also scales from the pure λcalculi to the richer calculi with simple congruence proofs. 1
Relational Reasoning about Functions and Nondeterminism
, 1998
"... Reproduction of all or part of this work is permitted for educational or research use on condition that this copyright notice is included in any copy. See back inner page for a list of recent BRICS Dissertation Series publications. Copies may be obtained by contacting: BRICS ..."
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Cited by 31 (4 self)
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Reproduction of all or part of this work is permitted for educational or research use on condition that this copyright notice is included in any copy. See back inner page for a list of recent BRICS Dissertation Series publications. Copies may be obtained by contacting: BRICS
Modelling dynamic Web data
 Imperial College London
, 2003
"... We introduce the Xdπ calculus, a peertopeer model for reasoning about dynamic web data. Web data is not just stored statically. Rather it is referenced indirectly, for example using hyperlinks, service calls, or scripts for dynamically accessing data, which require the complex coordination of data ..."
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Cited by 22 (3 self)
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We introduce the Xdπ calculus, a peertopeer model for reasoning about dynamic web data. Web data is not just stored statically. Rather it is referenced indirectly, for example using hyperlinks, service calls, or scripts for dynamically accessing data, which require the complex coordination of data and processes between sites. The Xdπ calculus models this coordination, by integrating the XML data structure with process orchestration techniques associated with the distributed picalculus. We study behavioural equivalences for Xdπ, to analyze the various possible patterns of data and process interaction.
Relational Reasoning about Contexts
 HIGHER ORDER OPERATIONAL TECHNIQUES IN SEMANTICS, PUBLICATIONS OF THE NEWTON INSTITUTE
, 1998
"... ..."
A Survey of Semantic Techniques for Active Networks
, 1997
"... Active networks open up switches within the network to allow computation upon them. Because these switches are public resources, and are essential to the proper and correct running of many important systems, the safety and security requirements placed upon the computation environment must be much st ..."
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Cited by 10 (0 self)
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Active networks open up switches within the network to allow computation upon them. Because these switches are public resources, and are essential to the proper and correct running of many important systems, the safety and security requirements placed upon the computation environment must be much stricter than in many other environments. In this paper we describe the motivation for some basic system decisions and show how recent advances in the semantics of programming languages can meet the safety challenges presented by the system yet still provide good performance. As the corollary to this point, we argue that the construction of proofs over programs is a difficult thing to do, and should be left to the designer of the programming language and not the programmer. 1 What are active networks? Most networks currently have a topology where `smart' hosts sit at the edges of the network, and are connected by `dumb' switches: H H H H H R R R H R Active nodes Host Router Passive nodes In...