The convergence of Internet of Things (IoT) and the Cloud has significantly facilitated the provision and management of services in large-scale applications such as smart cities. With a huge number of IoT services accessible through clouds, it is very important to model and expose cloud-based IoT services in a scalable manner, promising easy and realtime delivery of smart city services. The existing work in this area does not sufficiently address this design issue due to the adoption of a uniform and flat view to the structure of IoT services and their data in the Cloud. In this paper, we propose a framework for scalable and realtime provisioning of cloud-based IoT services in large-scale applications, such as smart cities. These two features are achieved by structuring the description of IoT services in a hierarchical model and populating them in a tree structure containing references to services and their realtime data. Such a service access structure can be obtained based on logical or contextual scopes of a service. Using this approach, smart city applications can access IoT services and subscribe to their realtime data in an scalable manner at different contextual levels, e.g., from a municipal district to a street.
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