New technical report on types for mobile agents

The use of types to control the mobility of distributed agents, 
and the effect of these types on agent equivalence, should make the
following technical report of interest to subscribers to the theory
mailing list.

Available from http://www.cogs.susx.ac.uk/reports/

Title:      Towards a behavioural theory of access and mobility control
            in distributed systems
Author(s):  Matthew Hennessy, Massimo Merro, Julian Rathke
Report:     Computer Science Report 2002:01
Issued:     University of Sussex, Brighton BN1 9QH, October 2002
Abstract:   We define a typed bisimulation equivalence for the language
            Dpi, a distributed version of the pi-calculus in which
            processes may migrate between dynamically created locations.
            It takes into account resource access policies, which can be
            implemented in Dpi using a novel form of dynamic capability
            types. The equivalence, based on typed actions between
            configurations, is justified by showing that it is
            fully-abstract with respect to a natural distributed version
            of a contextual equivalence. In the second part of the paper
            we study the effect of controlling the migration of
            processes. This affects the ability to perform observations
            at specific locations, as the observer may be denied access.
            We show how the typed actions can be modified to take this
            into account, and generalise the full-abstraction result to
            this more delicate scenario.