Description
The diffusion of portable client devices is promoting the spreading of novel mobile services, both traditional such as email and printing, and new such as social computing applications, capable of opportunistically exploiting any computing resource and any wireless connectivity encountered by roaming users. The new requirements call for novel context-aware middlewares to support and simplify the retrieval and the usage of context data. However, existing context data dissemination infrastructures still present several limitations: they are unable to adaptively exploit impromptu any wireless communication opportunity; they are unable to scale, especially in wide/densely populated environments; and they are prone to connection/device flaws. The article proposes a novel context-aware middleware that achieves adaptability, scalability, and dependability in context data dissemination through three main core guidelines: by using a distributed hierarchical architecture, by employing lightweight and adaptive context data dissemination solutions, and by adopting statistical context data/query replication techniques. The performance results, obtained by extensively testing the proposed solution in our wireless university campus testbed, have validated our design choices.