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We investigate the interactions of subtyping and recursive types, in a simply typed λ-calculus. The two fundamental questions here are whether two (recursive)types are in the subtype relation and whether a term has a type. To address the first question, we relate various definitions of type equivalence and subtyping that are induced by a model, an(More)
Our objective is to understand the notion of <I>type</I> in programming languages, present a model of typed, polymorphic programming languages that reflects recent research in type theory, and examine the relevance of recent research to the design of practical programming languages. Object-oriented languages provide both a framework and a motivation for(More)
The Ambient Calculus is a process calculus where processes may reside within a hierarchy of locations and modify it. The purpose of the calculus is to study mobility, which is seen as the change of spatial configurations over time. In order to describe properties of mobile computations we devise a modal logic that can talk about space as well as time, and(More)
Statically-typed programming languages allow earlier error checking, better enforcement of disciplined programming styles, and generation of more efficient object code than languages where all type-consistency checks are performed at runtime. However, even in statically-type languages, there is often the need to deal with data whose type cannot be known at(More)
Java has demonstrated the utility of type systems for mobile code, and in particular their use and implications for security. Security properties rest on the fact that a well-typed Java program (or the corresponding verified bytecode) cannot cause certain kinds of damage.In this paper we provide a type system for mobile computation, that is, for computation(More)
This paper presents a simulation algorithm for the stochastic pi-calculus, designed for the efficient simulation of biological systems with large numbers of molecules. The cost of a simulation depends on the number of species, rather than the number of molecules, resulting in a significant gain in efficiency. The algorithm is proved correct with respect to(More)