Maintaining coherent views over dynamic distributed data
ICDCIT'10 Proceedings of the 6th international conference on Distributed Computing and Internet Technology
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Applications that monitor functions over rapidly and unpredictably changing data, express their needs as continuous queries. Our focus is on a rich class of queries, expressed as polynomials over multiple data items. Given a set of polynomial queries at a coordinator C, and a user-specified accuracy bound (tolerable imprecision) for each query, we address the problem of assigning data accuracy bounds or filters to the source of each data item. Assigning data accuracy bounds for non-linear queries poses special challenges. Unlike linear queries, data accuracy bounds for non-linear queries depend on the current values of data items and hence need to be recomputed frequently. So, we seek an assignment such that a) if the value of each data item at C is within its data accuracy bound then the value of each query is also within its accuracy bound, b) the number of data refreshes sent by sources to C to meet the query accuracy bounds, is as low as possible, and c) the number of times the data accuracy bounds need to be recomputed is as low as possible. In this paper, we couple novel ideas with existing optimization techniques to derive such an assignment.