Updates of Relational Views

The problem of translating updates of database views is studied. View updates are disambiguated by requiring that a specified view complement (i.e., a second view that contains all the information omitted from the given view) remain constant during the translation. Some of the computational problems related to the apphcafion of this general methodology in the context of relational databases are studied. Projective views of databases that consist of a single relation and satisfy funcuonal dependencies are emphasized. After characterizing complementary views, the authors show that finding a minimum complement of a given view is NP-complete. The problem of translating the insertion of a tuple into a view is then studied in detail, and the results are extended to the cases of deletion and replacement of a tuple. Finally, the explicit functional dependencies, a new kind of dependency that intuitively states that some part of the database information can be computed from the rest, are defined and studied.