Research problems in data warehousing
CIKM '95 Proceedings of the fourth international conference on Information and knowledge management
Efficient Snapshot Differential Algorithms for Data Warehousing
VLDB '96 Proceedings of the 22th International Conference on Very Large Data Bases
Modeling a faster data warehouse
IDEAS'97 Proceedings of the 1997 international conference on International database engineering and applications symposium
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Detecting and extracting modifications from information sources is an integral part of data warehousing. For unsophisticated sources, in practice it is often necessary to infer modifications by periodically comparing snapshots of data from the source. Although this em snapshot differential problem is closely related to traditional joins and outerjoins, there are significant differences, which lead to simple new algorithms. In particular, we present algorithms that perform (possibly lossy) compression of records. We also present a {\em window} algorithm that works very well if the snapshots are not ``very different.'''' The algorithms are studied via analysis and an implementation of two of them; the results illustrate the potential gains achievable with the new algorithms.