Dealing with Uncertainty in Mobile Publish/Subscribe Middleware

Because of its loose coupling between event producers and consumers, publish/subscribe (pub/sub) middleware has many advantages when implementing systems for spontaneous, ad-hoc, pervasive applications. One main aspect of such applications is device mobility, but unfortunately, most of the current pub/sub systems do not adequately support mobile clients. Mobility has two orthogonal aspects: physical mobility is concerned with location transparency (i.e., roaming clients) while logical mobility deals with location awareness (i.e., subscriptions are automatically adapted to a client’s current location). To efficiently support mobility, it is necessary to adequately deal with the uncertainty introduced by client movement. This paper sketches how this is done in the existing pub/sub middleware REBECA and shows how to increase the efficiency of logical mobility by adapting the implementation of physical mobility. The paper closes with a list of open research issues related to the use of pub/sub middleware in the context of mobile and pervasive computing.