Efficient database updates with independent schemes

The weak instance model is a framework for considering the relations in a d atabase as a whole, regardless of the way attributes are grouped in the ind ividual relations. Queries and updates can be performed for any set of attr ibutes. The management of updates is based on a lattice structure on the se t of legal states, and inconsistencies and ambiguities can arise. In the general case, the test for consistency and determinism may involve t he whole database. In this paper it is shown how, for the highly significan t class of independent schemes, updates can be handled efficiently, conside ring only the relevant portion of the database.