On the Distributability of Mobile Ambients (Technical Report)

TL;DR

This paper analyzes the distributed capabilities of mobile ambients, showing they are not fully distributable due to limited synchronization expressiveness compared to pi-calculus, and discusses creating a fully distributed variant.

Contribution

It provides a formal analysis of mobile ambients' synchronization capabilities and establishes their position between pi-calculus and join-calculus in expressive power.

Findings

Mobile ambients can express the M synchronization pattern.

They cannot fully encode pi-calculus, limiting their distributability.

Results suggest ways to develop a fully distributed mobile ambient variant.

Abstract

Modern society is dependent on distributed software systems and to verify them different modelling languages such as mobile ambients were developed. To analyse the quality of mobile ambients as a good foundational model for distributed computation, we analyse the level of synchronisation between distributed components that they can express. Therefore, we rely on earlier established synchronisation patterns. It turns out that mobile ambients are not fully distributed, because they can express enough synchronisation to express a synchronisation pattern called M. However, they can express strictly less synchronisation than the standard pi-calculus. For this reason, we can show that there is no good and distributability-preserving encoding from the standard pi-calculus into mobile ambients and also no such encoding from mobile ambients into the join-calculus, i.e., the expressive power of mobile ambients is in between these languages. Finally, we discuss how these results can be used to obtain a fully distributed variant of mobile ambients.