A new basis for the weak instance model
Paolo Atzeni, Maria Cristina De Bernardis · 1987
A new definition of the weak instance model is presented, which does not consider the missing values as existent though unknown, but just assumes that no information is available about them. It is possible to associate with the new definition logical theories that do not contain universally quantified variables. The new model enjoys various desirable properties of the old weak instance model, with respect to dependency satisfaction, query answering, and associated logical theories.