The Internet of Things (IoT) is characterized by a wide penetration in the regular user's life through an increasing number of Things embedding sensing, actuating, processing, and communication capacities. A considerable portion of those Things will be mobile Things, which come with several advantages yet lead to unprecedented challenges. The most critical challenges, that are directly inherited from, yet amplify, today's Internet issues, lie in handling the large scale of users and mobile Things, providing interoperability across the heterogeneous Things, and overcoming the unknown dynamic nature of the environment, due to the mobility of an ultra-large number of Things. This thesis addresses the aforementioned challenges by revisiting the commonly employed Service-Oriented Architecture (SOA) which allows the functionalities of sensors/actuators embedded in Things to be provided as services, while ensuring loose-coupling between those services and their hosts, thus abstracting their heterogeneous nature. In spite of its benefits, SOA has not been designed to address the ultra-large scale of the mobile IoT. Consequently, our main contribution lies in conceiving a Thing-based Service-Oriented Architecture, that revisits SOA interactions and functionalities, service discovery and composition in particular. We concretize the novel architecture within MobIoT, a middleware solution that is specifically designed to manage and control the ultra-large number of mobile Things in partaking in IoT-related tasks. To assess the validity of our proposed architecture, we provide a prototype implementation of MobIoT and evaluate its performance through extensive experiments that demonstrate the correctness, viability, and scalability of our solution.
