5. Conclusions

[Ull89] Ullman, J.D. "Principles of database and knowledge-base systems", volumes 1 and 2. [Urp93] Urpí, T "El mètode dels esdeveniments interns per al càlcul de canvis en bases de dades deductives", Ph.D. thesis, Universitat Politècnica de Catalunya, Barcelona, 1993, (in catalan). implication mentioned before δProduct(p,n) → δAux2(p) and δAux2(p) → ¬ ∃s Supplier n (s,p) and, thus, Supplier n (s,p) will be false. We have reviewed the Internal Events Method for change computation in deductive databases. That method derives rules that compute efficiently the changes induced by an update, but it takes into account only the knowledge given by primary key integrity constraints. In the paper, we have extended the method by considering four additional integrity constraints:-Alternate keys constraints-Exclusion dependencies-Inclusion dependencies-Referential integrity constraints We have shown that the knowledge derived from such integrity constraints can simplify the change computation rules, thus obtaining a significant improvement in performance. We already have implemented the automatic generation of the transition and internal events rules taking into account the primary and alternate key constraints. We plan to further formalize the new simplifications, to study the order of their application, which may depend of the extensional database, and to implement them. Acknowledgements We would like to thank to