Imprecise and uncertain information in databases: an evidential approach

A novel approach for representing imprecise and uncertain data and evaluating queries in the framework of an extended relational database model based on the Dempster-Shafer theory of evidence is proposed. Because of the ability to combine evidences from different sources, the semantics of the update operation of imprecise or uncertain data is reconsidered. By including an undefined value in a domain, three different cases of a null value are presented: unknown, inapplicable, and unknown or inapplicable. In this model, two levels of uncertainty in the database are supported: one is for the attribute value level and the other is for the tuple level