International Research Publication House (IRPH)
A Data Warehouse (DW) is a repository of information retrieved from multiple, possibly heterogeneous, autonomous, distributed database and other information sources for the purpose of complex querying, analysis, and decision support. Data in the DW are selectively collected from the sources, processed in order to resolve inconsistencies, and integrated advance (at design time) before data loading. DW data are usually organized multi-dimensionally to support On-Line Analytical Processing (OLAP). A DW can be seen abstractly as a set of materialized views defined over the source relations.