Complements for data warehouses

Views over databases have recently regained attention in the context of data warehouses, which are seen as materialized views. In this setting, efficient view maintenance is an important issue, for which the notion of self-maintainability has been identified as desirable. We extend self-maintainability to (query and update) independence, and we establish an intuitively appealing connection between warehouse independence and view complements. Moreover, we study minimal complements and show how to compute them in the presence of key constraints and inclusion dependencies in the underlying databases. Taking advantage of these complements, an algorithm is outlined for the specification of independent warehouses.