Tessa Daniel

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.

Towards a Trusted Compiler for a Query Language for Wireless Sensor Networks.

Efficient and reliable information extraction in wireless sensor networks continues to be an area of abundant research. Current investigations follow two general themes: agent-based systems and query-based systems. The ASQue Sensor Query language (ASQue) was put forward by the Cogent Computing Research Centre as an applicative query language specifically designed to address the particular constraints imposed by sensor networks. A parser for the language and its formal specification were seen as an essential first step in being able to issue correct, purposeful queries to the network. A simple specification model that could be incrementally refined through to implementation was considered essential in accomplishing this goal. The purpose of this paper, therefore, is two-fold. First, to report the motivation for the formal specification of the ASQue parser, and second, to describe the construction of the parser from specification to implementation using the B-method.