Incremental computation of set difference views

Views can be computed by means of recomputation or they can be computed incrementally. Incremental view computation outperforms view recomputation in many situations. This is particularly true in distributed database environments such as data warehousing environments. The authors present and analyze two algorithms for the incremental computation of relational set difference views. Set differences occur naturally in the definition of the set-division operator and in rewritten nested queries. The I/O efficiency of the incremental algorithms is compared to each other and to efficient recomputation algorithms. The cost analysis strongly indicates that incremental computation of set difference views outperforms recomputation of set difference views in many situations.