Updating under integrity constraints in fuzzy databases

Update operations considering unacceptable elements are addressed under integrity constraints in a fuzzy relational database based on necessity and possibility measures. If one has no constraints in a database, the results of update operations are unconditionally accepted in the database. As a matter of fact, databases are constructed under integrity constraints necessarily. Thus any update operation must be performed under imposed integrity constraints. The most fundamental unit is a possible value in the fuzzy relational database where attribute values are expressed by possibility distributions. The possible value is associated with another one through integrity constraints. The effects of an update operation are propagated from a possible value to another one through integrity constraints to keep databases consistent. This corresponds to creating unacceptable components. However, by considering the removal of unacceptable components, one avoids the unacceptable elements in results obtained by the update operations