Laboratory We introduce a calculus describing the movement of processes and devices, including movement through administrative domains.

We study a variant of Levi and Sangiorgi's Safe Ambients (SA) enriched with passwords (SAP). In SAP by managing passwords, for example generating new ones and distributing them selectively, an ambient may now program who may migrate into its computation space, and when. Moreover in SAP an ambient may provide different services depending on the passwords exhibited by its incoming clients. We give an lts based operational semantics for SAP and a labelled bisimulation based equivalence which is proved to coincide with barbed congruence. Our notion of bisimulation is used to prove a set of algebraic laws which are subsequently exploited to prove more significant examples. 1

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Abstract. We extend the modal logic of ambients described in [7] to the full ambient calculus, including name restriction. We introduce logical operators that can be used to make assertions about restricted names, and we study their properties. 1

We settle the complexity bounds of the model checking problem for the ambient calculus with public names against the ambient logic. We show that if either the calculus contains replication or the logic contains the guarantee operator, the problem is undecidable. In the case of the replication-free calculus and guarantee-free logic we prove that the problem is PSPACE-complete. For the complexity upper-bound, we devise a new representation of processes that remains of polynomial size during process execution; this allows us to keep the model checking procedure in polynomial space. Moreover, we prove PSPACE-hardness of the problem for several quite simple fragments of the calculus and the logic; this suggests that there are no interesting fragments with polynomial-time model checking algorithms.

We present a new version of the Seal Calculus, a calculus of mobile computation. We study observational congruence and bisimulation theory, and show how they are related.

We study the behavioural theory of Cardelli and Gordon's Mobile Ambients. We give an LTS based operational semantics, and a labelled bisimulation based equivalence that coincides with reduction barbed congruence. We also provide two up-to proof techniques that we use to prove a set of algebraic laws, including the perfect firewall equation.

Abstract. We define a variant of Lamport’s Temporal Logic of Actions, extended by spatial modalities, that is intended for the specification of mobile systems with distributed state. We discuss notions of refinement appropriate for mobile systems, specifically concerning the topological structure of the system, and show how these can be represented in the logic via quantification and implication, ensuring transitivity and compositionality of refinements. 1

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In addition to behavioral properties, spatial logics can talk about other key properties of concurrent systems such as secrecy, freshness, usage of resources, and distribution. We study an expressive spatial logic for systems specified in the synchronous pi-calculus with recursion, based on a small set of behavioral and spatial observations. We give coinductive and equational characterizations of the equivalence induced on processes by the logic, and conclude that it strictly lies between structural congruence and strong bisimulation. We then show that model-checking is decidable for a useful class of processes that includes the finite-control fragment of the pi-calculus.