A Distributed Garbage Collector with Diffusion Tree Reorganisation and Mobile Objects

We present a new distributed garbage collection algorithm that is able to reorganise diffusion trees and to support mobile objects. It has a modular design comprising three components: a reliable transport mechanism, a referencecounting based distributed garbage collector for non-mobile objects, and an extra layer that provides mobility. The algorithm is formalised by an abstract machine and is proved to be correct. The safety property ensures that an object may not be reclaimed as long as it is referred to locally or remotely. The liveness property guarantees that unreachable objects will eventually be reclaimed. The mobility property certifies that messages are always forwarded towards more recent mobile object positions.