A Correct Abstract Machine for Safe Ambients

Abstract

International audienceWe describe an abstract machine, called GcPan, for the dis- tributed execution of Safe Ambients (SA), a variant of the Ambient Calculus (AC).Our machine improves over previous proposals for executing AC, or variants of it, mainly through a better management of special agents (forwarders), created upon code migration to transmit messages to the target location of the migration.We establish the correctness of our machine by proving a weak bisimilarity result with a previous abstract machine for SA, and then appealing to the correctness of the latter machine.More broadly, this study is a contribution towards understanding issues of correctness and optimisations in implementations of distributed languages encompassing mobility

Pict correctness revisited

“…There have been several recent papers devoted to the formal description of implementations of process calculi based on the π-calculus or the Ambient calculus. In addition to Pict, one can notably cite the Jocaml distributed implementation of the Join calculus [6,5], the Join calculus implementation of Mobile Ambients [7], Nomadic Pict [22,20], the abstract machine for the M-calculus [10], the Fusion Machine [8], the PAN and GCPAN abstract machines for Safe Ambients [11,12], the CAM abstract machine for Channel Ambients [15] and the abstract machine for the Kell calculus [1]. Most of these works [7,22,20,10,8,11,12,15,1] deal with distributed implementations of calculi, rather than local implementation of concurrent processes like in Pict.…”

Abstract Machines for Safe Ambients in Wide-Area and Mobile Networks

“…To handle such situations, we enriched Pan mov with the mechanism used in GcPan [8]; it reclaims unused forwarders and contracts forwarder chains. The following are the basic ideas of GcPan: (1) to detect unused forwarders, every agent is equipped with a reference count.…”

“…If an agent is a forwarder whose count is zero, it is reclaimed, and (2) to contract forwarder chains, using Tarjan's union-find algorithm [14], every agent is relocated immediately below its parent ambient. For a detailed understanding of GcPan, see [8].…”

“…The fact that Pan is a correct implementation of SA, i.e., SA and Pan are weak barbed bisimilar, is proved in [12,7]; hence, it suffices to prove that Pan and Pan mov are weak barbed bisimilar. We follow the proof method between Pan and GcPan [8,9]. Proof.…”

“…Several studies have been carried out on the distributed implementation of Ambient-like calculi [1,4,12,8,11,13]. Among 1.…”