Imprecision and Uncertainty in Database Systems

Databases are models of the real world. Yet, our knowledge of the real world is often imperfect, thus challenging our ability to create databases of integrity. To uphold the integrity of a database in situations where knowledge of the real world is imperfect, one may either (1) restrict the model to that portion of the real world about which perfect information is available, or (2) develop formalisms that allow the representation of imperfect information. This paper surveys some of the better-known database formalisms for capturing imperfect information. Imperfections in the specification and processing of transactions also have important impact on the quality of the information delivered to users, and this survey discusses them as well.