Materialized views in data warehousing environments

We discuss the use of materialized views in the construction and maintenance of data warehousing environments. Although materializing views represents the most effective technique to improve OLAP (on-line analytical processing) query performance, it introduces particular challenges into these environments: (i) identification of which views to materialize, considering the trade-off among performance, scalability and view maintenance restrictions; and (ii) incremental maintenance of these views. In addition to analyzing and comparing some current proposals aimed at solving these two challenges, we also identify restrictions in the surveyed proposals to a Web distributed data warehousing environment, in which the warehouse data are fragmented, replicated and allocated through several sites. Some suggestions are made to overcome such restrictions.