Expiring Data in a Warehouse

Data warehouses collect data into materialized views for analysis. After some time, some of the data may no longer be needed or may not be of interest. In this paper, we handle this by expiring or removing unneeded materialized view tuples. A framework supporting such expiration is presented. Within it, a user or administrator can declaratively request expirations and can specify what type of modifications are expected from external sources. The latter can significantly increase the amount of data that can be expired. We present efficient algorithms for determining what data can be expired (data not needed for maintenance of other views), taking into account the types of updates that may occur. Keywords: materialized views, data warehousing 1 Introduction Materialized views are often used to store warehouse data. The amount of data copied into these views may be very large; for instance, [JMS95] cites a major telecommunications company that collects 75GB of detailed call data every da..