The weak instance model is a framework to consider the relations in a database as a whole, regardless of the way attributes are grouped in the individual relations. Queries and updates can be performed involving any set of attributes. The management of updates is based on a lattice structure on the set of legal states, and inconsistencies and ambiguities can arise
In the general case, the test for inconsistency and determinism may involve the application of the chase algorithm to the whole database. In this paper it is shown how, for the highly significant class of independent schemes, updates can be handled efficiently, considering only the relevant portion of the database.
