The Internet of Things (IoT) envisions that objects may be connected to the Internet, producing and consuming data in real-time. Today, numerous middleware platforms are available to facilitate the communication with these objects. Unfortunately, the interoperability of these platforms is very limited because it requires to "manually" connect the services proposed by each platform. One key design goal for our contribution is not to build yet another middleware, but rather to augment the functionalities of existing systems via an extension to support their integration into a network of heterogeneous IoT hubs. The extension includes a RESTful API to manipulate the basic component of our extension, the IoT feeds. The IoT feeds allow the platform's owner to dynamically marshal the IoT features connected to the platform, as well as the data that they produce. Furthermore, the feeds enable the owner to manage and control the data flows before connecting them to his applications. Subsequently, these feeds may also be published to meta-hubs in order to expose them to third parties. We evaluated an implementation our extension for Android systems to show the feasibility of managing the data flows using the RESTful API on this platform.
However, a number of challenges, such as service composition, data-points availability, service discovery or data accuracy, have been highlighted in @cite_10 @cite_11 @cite_5 to create interoperable service-oriented IoT solutions. Unfortunately, these challenges have not been addressed by today's IoT solutions.
@cite_5 @cite_10 @cite_11
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The Internet of Things plays a central role in the foreseen shift of the Internet to the Future Internet, as it incarnates the drastic expansion of the Internet network with non-classical ICT devices. It will further be a major source of evolution of usage, due to the penetration in the user's life. As such, we envision that the Internet of Things will cooperate with the Internet of Services to provide users with services that are aware of their surrounding environment. The supporting service-oriented middleware shall then abstract the functionalities of Things as services as well as provide the needed interoperability and flexibility, through a loose coupling of components and composition of services. Still, core functionalities of the middleware, namely service discovery and composition, need to be revisited to meet the challenges posed by the Internet of Things. Challenges in particular relate to the ultra large scale, heterogeneity and dynamics of the Internet of Things that are far beyond the ones of today's Internet of Services. In addition, new challenges also arise, pertaining to the physical-world aspect that is central to the IoT. In this paper, we survey the major challenges posed to service-oriented middleware towards sustaining a service-based Internet of Things, together with related state of the art. We then concentrate on the specific solutions that we are investigating within the INRIA ARLES project team as part of the CHOReOS European project, discussing new approaches to overcome the challenges particular to the Internet of Things. As the Internet of Things (IoT) grows in interest from both research and industrial parts, the lack of standard solutions to quickly and easily build and install IoT applications becomes a topic of high interest. In this paper, we introduce a language called SALT (Simple Application Logic description using Transducers) that allows describing and deploying the distributed logic needed in order to fulfil a complete desired application. This language aims at giving extended functionalities by filling the gap between the logical capabilities offered by services orchestration and the closeness efficiency of services choreography. SALT is interpreted by a virtual machine running on devices that introduces an abstraction layer in order to simplify access to hardware capabilities. SALT implements several mechanisms to comply with organisation issues presented in the Services Oriented Computing realm dealing with Services interactions, adapted to the specific constraints of the IoT. This work details SALT's concepts, formalism and implementation.