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SEM: LUCA CARDELLI, UNI GENEVE, 

Abstractions for Mobile Computation

par Luca Cardelli,

Digital Equipment Corporation, Systems Research Center

Uni Bastion, salle B 104, � 16h15
Vendredi 27 Juin 

ABSTRACT

There are two distinct areas of work in mobility: "mobile computing", 
concerning computation that is carried out in mobile devices, and "mobile 
computation", concerning mobile code that moves between devices. These 
distinctions are destined to vanish. We aim to describe all aspects of 
mobility within a single framework that encompasses mobile agents, the 
ambients where agents interact and the mobility of the ambients themselves.

The main difficulty with mobile computation is not in mobility per se, but in 
the crossing of administrative domains. Mobile programs must be equipped to 
navigate a hierarchy of domains, at every step obtaining authorization to move 
further. Therefore, at the most fundamental level we need to capture notions 
of locations, of mobility and of authorization to move.

We identify "mobile ambients" as a fundamental abstraction that generalizes 
both dynamic agents and the static domains they must cross. From a formal 
point of view we develop a simple but computationally powerful calculus that 
directly embodies domains and mobility (and little else). The calculus forms 
the basis of a small-language/ Java-library. We demonstrate the expressiveness 
of the approach by a series of examples, including showing how a notion such 
as "crossing a firewall" has a direct and analyzable interpretation.