256 research outputs found
Security Policies as Membranes in Systems for Global Computing
We propose a simple global computing framework, whose main concern is code migration. Systems are structured in sites, and each site is divided into two parts: a computing body, and a membrane which regulates the interactions between the computing body and the external environment. More precisely, membranes are filters which control access to the associated site, and they also rely on the well-established notion of trust between sites. We develop a basic theory to express and enforce security policies via membranes. Initially, these only control the actions incoming agents intend to perform locally. We then adapt the basic theory to encompass more sophisticated policies, where the number of actions an agent wants to perform, and also their order, are considered
Explicit fairness in testing semantics
In this paper we investigate fair computations in the pi-calculus. Following
Costa and Stirling's approach for CCS-like languages, we consider a method to
label process actions in order to filter out unfair computations. We contrast
the existing fair-testing notion with those that naturally arise by imposing
weak and strong fairness. This comparison provides insight about the
expressiveness of the various `fair' testing semantics and about their
discriminating power.Comment: 27 pages, 1 figure, appeared in LMC
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