A gossip protocol to support service discovery with heterogeneous ontologies in MANETs

Service discovery in mobile ad hoc networks (MANETs) is an integral part for collective application interoperability. The discovery process must cope not only with transient communication but also with an environment where autonomous mobile nodes act as both service providers and consumers. Imposing prede ned service interfaces in such an unpredictable and dynamic environment is an inapppropriate assumption. A more exible description and discovery mechanism can be provided with the use of ontologies and semantic reasoning. Assuming that services are described by heterogeneous ontologies poses many technical challenges but is more realistic than requiring a single domain ontology. In particular, a mechanism is required to match the different ontologies and make provided services available to all nodes. In this paper we present a model to support semantic service discovery in MANETs. A core part of the model is the distributed approach to ontology matching. We rely on the use of a novel gossip protocol that offers an even utilisation of physical resources across the participating nodes. This makes the model suitable for resource constraint mobile devices. We present the gossip protocol and an evaluation that shows the good scalability and discovery properties of the protocol

Probabilistic discovery of semantically diverse content in MANETs

Mobile ad hoc networks rely on the opportunistic interaction of autonomous nodes to form networks without the use of infrastructure. Given the radically decentralised nature of such networks, their potential for autonomous communication is significantly improved when the need for a priori consensus amongst the nodes is kept to a minimum. This paper addresses an issue within the domain of semantic content discovery, namely, its current reliance on the preexisting agreement between the schema of content providers and consumers. We present OntoMobil, a semantic discovery model for ad hoc networks that removes the assumption of a globally known schema and allows nodes to publish information autonomously. The model relies on the randomised dissemination and replication of metadata through a gossip protocol. Given schemas with partial similarities, the randomised metadata dissemination mechanism facilitates eventual semantic agreement and provides a substrate for the scalable discovery of content. A discovery protocol can then utilise the replicated metadata to identify content within a predictable number of hops using semantic queries. A stochastic analysis of the gossip protocol presents the different trade-offs between discoverability and replication. We evaluate the proposed model by comparing OntoMobil against a broadcast-based protocol and demonstrate that semantic discovery with proactive replication provides good scalability properties, resulting in a high discovery ratio with less overhead than a reactive non-replicated discovery approach