Incremental recomputation of active relational expressions

Database updates are small and incremental compared to database contents. It is therefore desirable that recomputations of active relational expressions-such as views, derived data, integrity constraints, active queries, and monitors-can also be performed incrementally. An efficient algorithm for the incremental recomputation of active relational expressions based on finite differencing techniques is presented. Database updates are modeled as incremental changes to database relations, and the algorithm derives, by update propagation, the minimal incremental relational expressions that need recomputation. The algorithm has applications in the maintenance of materialized views and derived data, the checking of integrity constraints, and the evaluation of active queries and monitors