Currency-based updates to distributed materialized views

In currency-based updates, processing a query to a materialized view has to satisfy a currency constraint which specifies the maximum time lag of the view data with respect to a transaction database. Currency-based update policies are more general than periodical, deferred, and immediate updates; they provide additional opportunities for optimization and allow updating a materialized view from other materialized views. Algorithms for determining the source and timing of view updates and validating the resulting cost savings through simulation results are presented