Query optimization in information integration for queries involving aggregation and group by
Wejdan Alkaldi, Fereidoon Sadri · 2011
This paper addresses the efficient processing of queries involving aggregation and group-by in the semantic-model approach to information integration. Query processing algorithms materialization, subqueries, and wrapper have been extended for such aggregate queries. Algorithms have been presented for two cases: In the first case information at different sources are disjoint, while in the second case information sources may contain overlapping information.