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Context aware applications, which can adapt their behaviors to changing environments, are attracting more and more attention. To simplify the complexity of developing applications, context aware middleware, which introduces context awareness into the traditional middleware, is highlighted to provide a homogeneous interface involving generic context management solutions. This paper provides a survey of state-of-the-art context aware middleware architectures proposed during the period from 2009 through 2015. First, a preliminary background, such as the principles of context, context awareness, context modelling, and context reasoning, is provided for a comprehensive understanding of context aware middleware. On this basis, an overview of eleven carefully selected middleware architectures is presented and their main features explained. Then, thorough comparisons and analysis of the presented middleware architectures are performed based on technical parameters including architectural style, context abstraction, context reasoning, scalability, fault tolerance, interoperability, service discovery, storage, security & privacy, context awareness level, and cloud-based big data analytics. The analysis shows that there is actually no context aware middleware architecture that complies with all requirements. Finally, challenges are pointed out as open issues for future work.

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In the twenty-first century, the impact of wireless and ubiquitous technologies is changing the way people perceive and interact with the physical world. These communication paradigms promise to change and redefine, in a reasonably short period of time, the most common way of our everyday living. The continuous advances in the field of Wireless Sensor Networks and their direct application in Smart Spaces are clear examples of it. However, in order for this kind of new generation infrastructures to have a large-scale dissemination, there are still some open issues to tackle. In this way, this paper presents nSOM, a service-oriented framework based on sensor network design that provides internetworking services with the Internet cloud. This lightweight middleware architecture implements an agent-based virtual sensor service approach which is a compact semantic knowledge management scheme based on a dynamic composition model.

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