Complex query processing in wireless sensor networks

Greater availability and affordability of wireless technology has led to an increase in the number of wireless sensor network (WSN) applications where sense data is collected at a central user point, commonly outside the network (geographically and topologically) for processing. Resource constraints on nodes in the network coupled with considerable redundancy in the data generated mean that applications have to be developed with an eye to maximising energy efficiency in order to extend network life. In-network computation, and in particular in-network information extraction from data, has been promoted as a technique for achieving this aim. In-network processing, however, has been limited to systems where at most, simple aggregate queries are evaluated, the results of which are communicated to the outside world. There is currently little research into how the idea of in-network processing can be extended and implemented to allow more complex queries to be resolved within the network. This paper examines key applicative query-based approaches that utilise in-network processing for query resolution, identifies their strengths and limitations and puts forward ideas for facilitating in-network complex query processing in WSNs. Finally, preliminary results of experiments, where in-network attribute-based logical abstractions are used for processing complex queries, are presented. Copyright 2007 ACM.