Elio Giovannetti

M3 mobility types for mobile processes in mobile ambients

Abstract We present an ambient-like calculus in which the open capability is dropped, and a new form of “lightweight” process mobility is introduced. The calculus comes equipped with a type system that allows the kind of values exchanged in communications and the access and mobility properties of processes to be controlled. A type inference procedure determines the “minimal” requirements to accept a system or a component as well typed. This gives a kind of principal typing. As an expressiveness test, we show that some well known calculi of concurrency and mobility can be encoded in our calculus in a natural way.

Notes on the elimination of conditions

In these notes we have described a method for eliminating equality tests from conditions in ctrs. Two applications have been shown: the first is the transformation of a conditional trs into an equivalent unconditional one; the second is the extension of the user syntax of K-LEAF, a logic+functional programming language.

The Relevance of Semantic Subtyping

We compare Meyer and Routleys minimal relevant logic B+ with the recent semantics- based approach to subtyping introduced by Frisch, Castagna and Benzaken in the definition of a type system with intersection and union. We show that - for the functional core of the system - such notion of subtyping, which is defined in purely set-theoretical terms, coincides with the relevant entailment of the logic B+.

Dynamic and Local Typing for Mobile Ambients

An ambient calculus with both static and dynamic types is presented, where the latter ones represent mobility and access rights that may be dynamically consumed and acquired in a controlled way. Novel constructs and operations are provided to this end. Type-checking is purely local, except for a global hierarchy that establishes which locations have the authority to grant rights to which: there is no global environment (for closed terms) assigning types to names. Each ambient or process move is subject to a double authorization, one static and the other dynamic: static type-checking controls (communication and) “active” mobility rights, i.e., where a given ambient or process has the right to go; dynamic type-checking controls “passive” rights, i.e., which ambients a given ambient may be crossed by and which processes it may receive.

From Böhm's Theorem to Observational Equivalences: an Informal Account

Abstract There are essentially two ways of looking at the computational behaviours of λ-terms. One consists in putting the term within a context (possibly of λ-calculus extensions) and observing some properties (typically termination). The other consists in reducing the term until some meaningful information is obtained: this naturally leads to a tree representation of the information implicitly contained in the original term. The paper is an informal overview of the role played by Bohms Theorem in these observations of terms.

On isomorphisms of intersection types

The study of type isomorphisms for different λ-calculi started over twenty years ago, and a very wide body of knowledge has been established, both in terms of results and in terms of techniques. A notable missing piece of the puzzle was the characterization of type isomorphisms in the presence of intersection types. While, at first thought, this may seem to be a simple exercise, it turns out that not only finding the right characterization is not simple, but that the very notion of isomorphism in intersection types is an unexpectedly original element in the previously known landscape, breaking most of the known properties of isomorphisms of the typed λ-calculus. In particular, isomorphism is not a congruence and types that are equal in the standard models of intersection types may be nonisomorphic.

Types for ambient and process mobility

We present a new kind of ambient calculus in which the open capability is replaced by direct mobility of generic processes. The calculus comes equipped with a labelled transition system in which types play a major role: this system allows us to show interesting algebraic laws. As usual, types express the communication, access and mobility properties of the modelled system, and inferred types express the minimal constraints required for the system to be well behaved.

Ambient Calculi with Types: A Tutorial

A tutorial introduction to the key concepts of ambient calculi and their type disciplines, illustrated through a number of systems proposed in the last few years, such as Mobile Ambients, Safe Ambients, Boxed Ambients, and other related calculi with types.

Type Inference for Mobile Ambients in Prolog

The type system for the ambient calculus M 3 [8] is presented in a new form that derives the type of a term with the minimal set of mobility assumptions, and is therefore more amenable than the original form to a translation into a type inference algorithm. From the new formulation a Prolog program is derived, which implements a type inference algorithm for M 3 analogous to the one previously specified through formal rules. The implementation exploits in the standard way the peculiarities of the logic programming paradigm, and is therefore, in a sense, more abstract than the original algorithm’s specification itself.

On Isomorphisms of Intersection Types

The study of type isomorphisms for different i¾?-calculi started over twenty years ago, and a very wide body of knowledge has been established, both in terms of results and in terms of techniques. A notable missing piece of the puzzle was the characterization of type isomorphisms in the presence of intersection types. While at first thought this may seem to be a simple exercise, it turns out that not only finding the right characterization is not simple, but that the very notion of isomorphism in intersection types is an unexpectedly original element in the previously known landscape, breaking most of the known properties of isomorphisms of the typed i¾?-calculus. In particular, types that are equal in the standard models of intersection types may be non-isomorphic.