Recovering Information from Summary Data

Data is often stored in summarized form, as a histogram of aggregates (COUNTs, SUMs, or AVeraGes) over speci ed ranges. We study how to estimate the original detail data from the stored summary. We formulate this task as an inverse problem, specifying a well-de ned cost function that has to be optimized under constraints. We show that our formulationincludes the uniformity and independence assumptions as a special case, and that it can achieve better reconstruction results if we maximize the smoothness as opposed to the uniformity. In our experiments on real and synthetic datasets, the proposed method almost consistently outperforms its competitor, improving the rootmean-square error by up to 20 per cent for stock price data, and up to 90 per cent for smoother data sets. Finally, we show how to apply this theory to a variety of database problems that involve partialinformation,such as OLAP, data warehousingandhistogramsinquery optimization. This research was partially funded by the Na...

• Type: Conference
• Year: 1997
• Where: VLDB
• Authors: Christos Faloutsos, H. V. Jagadish, Nikolaos Sidiropoulos
• Keywords: Database, Smoother Data Sets, Speci Ed Ranges, VLDB 1997, Well-de Ned Cost