A Semantic-aware Framework for Service Definition and Discovery in the Internet of Things Using CoAP

The future of machine-to-machine (M2M) communications relies on reusability, scalability, and interoperability of services. Internet of Things (IoT) aims to provide an environment where smart devices can easily expose their services, while providing accurate service discovery functionality for clients to consume them. Semantic-first approaches and service annotation techniques have already been studied in the service definition context and most of them leverage WSDL or RESTFul services. However, IoT environments, due to their heterogeneous nature and often constrained resources, demand a more flexible and scalable approach. In this paper, semantic annotation of services is supported through ontologies defined for API definition languages such as Swagger and RAML. We leverage the CoAP protocol and linked-data serialization format (JSON-LD) to represent services, entities, and properties in a semantic-aware framework. This enables intelligent discovery of services. A case study on reducing energy consumption in data centers is used to demonstrate the effectiveness of our proposed framework.