Efficient semantic-based IoT service discovery mechanism for dynamic environments

With the Internet of Things (IoT), we are facing a proliferation of connected devices distributed over a collection of geographical locations and offering new services to users referred to as IoT services. These services are highly heterogeneous, mobile due to devices mobility, and their number is growing fast. To facilitate IoT service search, some solutions rely on the use of Semantic Web technologies to create homogenous service descriptions to reason on and support accurate and flexible search through matching semantic service description. However, most existing approaches are centralized and fail to scale with respect to the number of advertised services due to the cost of semantic reasoning specially during the matching process to search services. The scalability of the system becomes more critical when dealing with mobile service. To address this issue, we present in this paper a distributed, semantic-based IoT service search system with service mobility support. It relies on a hierarchical network of semantic gateways that represent geographical locations and host semantic service descriptions. To answer a service query, our approach is based on request matching and forwarding though the use of routing tables and similarity thresholds. Based on defined metrics, recursive clustering and information aggregation are performed over the hierarchy of gateways to construct the routing tables. Experimental results show that our method enables to reduce greatly search cost with comparison to a centralized approach and has an acceptable search path length. Moreover, during service mobility, our system is able to maintain a scalable and efficient search through a continuous matching cost optimization process that we implemented and tested.