The introduction of mobile code in the pervasive computing environment provides a good opportunity for research in ways to enhance execution flexibility. We note that current mobile code is too heavyweight and not adaptive enough to be used in pervasive computing where devices are resourcelimited and heterogeneity is the norm. In this paper, we propose a new lightweight, component-based mobile agent system that can adapt to diverse devices and features resource saving as one of its aims. The system supports strong mobility of mobile code, which is a prerequisite for achieving system flexibility and good performance. The system discretize the transmission of code and execution states and relies on a scheme called state-on-demand (SOD) for the execution of the mobile code. We provide performance results to demonstrate the effectiveness of the SOD scheme.

The Æ�-calculus, a new calculus based on the �-calculus, is a model for mobile distributed computation. The Æ�-calculus can be used to specify applications, in order to reason about their security and correctness properties. The Æ � primitives have been been implemented as a Java API. The implementation in Java provides a means of bridging the gap between application specification and implementation. 1

Pervasive computing is undoubtedly the next wave in the computing industry. With the proliferation of popularity of Intelligent Appliances (IA), e.g. mobile phones and Personal Digital Assistances (PDAs), and wireless network technologies in the past few years, pervasive computing has suc-

Mobility is an important paradigm for modern distributed applications, where mobile code is supplied on demand and mobile components interact freely within a given network. However, mobile applications are difficult to develop: not only do they involve complex parallel interactions between multiple components, but they must also satisfy strict security requirements. One could argue that the development of such applications would benefit from a programming language based on a formal model. Foundational research has shown that Ambient calculi are a promising approach to modelling mobile computation. More recently, Boxed Ambient calculi have been designed to be at a level of abstraction suitable for an application programmer. This paper presents a programming language based on a variant of Boxed Ambients with channels. The paper shows how the language can be used to program a non-trivial mobile application for tracking the location of migrating agents, starting from a formal calculus specification of the application. The paper also describes how a distributed runtime for the language can be implemented in OCaml, based on a formal specification of the runtime that was proved sound and complete with respect to the calculus in [21]. The use of a functional language allows for an almost direct mapping from runtime specification to functional code, giving greater confidence in the runtime implementation. The correctness of the runtime ensures that the work done in specifying and analysing mobile applications is not lost during their execution. 1.

acceptée sur proposition du jury: Prof. A. Wegmann, président du jury Prof. M. Odersky, directeur de thèse