Approximate Query Answering by Model Averaging

In earlier work we have introduced and explored a variety of different probabilistic models for the problem of answering selectivity queries posed to large sparse binary data sets. These models can be directly scaled to hundreds or thousands of dimensions, in contrast to other approximate querying techniques (such as histograms or wavelets) that are inherently limited to relatively small numbers of dimensions. In this paper, we extend this work by applying probabilistic model-averaging to the problem of query answering, a scheme that allows the query-answering algorithm to automatically and optimally adapt to both the specific nature of the data and the distribution of queries being issued any specific user. We demonstrate that on realworld and simulated data sets that model-averaging can reduce the prediction error of any single model by factors of up to 50%. Learning the combining weights is a straightforward and scalable optimization problem that can be easily automated, providing a practical framework for approximate query answering with massive data sets.