Towards a Behavioural Theory of Access and Mobility Control in Distributed Systems

Abstract

Abstract. We define a typed bisimulation equivalence for the language Dpi, a distributed version of the π-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 fullyabstract 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.

Basic Observables for a Calculus for Global Computing

“…In (R-OUT) and (R-EVAL), the existence of a connection between the nodes source and target of the action is necessary to place the spawned component. Notice that existence of the connection can only be checked at run-time: an approach like [23] does not fit well in a global computing setting because it relies on a typing mechanism that would require to statically know the whole net. (R-IN) and (R-MATCH) additionally require the existence of a matching datum in the target node.…”

“…To this aim, dynamically evolving type environments could be exploited to constraint the behaviours of processes and the observations of an environment. Some work in this direction has been done in [23].…”

“…On the contrary, bisimulation-based equivalences have been studied to some extent. Bisimulation-based equivalences for calculi relying on a flat net topology are developed in [1,23]; such equivalences are mainly derived from bisimulation equivalences for the π-calculus and its variants. Bisimulationbased equivalences for calculi relying on a hierarchical net topology are developed in [28,8,10,24].…”

“…All foundational languages proposed in the literature intend migration as the movement either of processes or of some other entities having executable content (such as nodes themselves). Thus, the former languages model the network as an evolving graph of fully connected nodes (see e.g., Dπ-calculus [23], KLAIM [13], Nomadic Pict [40], π 1 -calculus [1]) whereas the latter ones model the network as an evolving forest of trees (see e.g., Ambient [9] and its variants, DJoin [18], Homer [24], M-calculus [38], Seal [10]). In our view, both approaches do not convincingly model global computers (the Internet is neither a clique nor a forest of trees) and lack of flexibility (e.g.…”

Proof Methodologies for Behavioural Equivalence in Dpi

“…In this section we recall the essential features of the language D; readers are referred to [HMR04,HR02b,CHR05] for a more detailed description.…”