A NEW TREATMENT OF INCOMPLETE INFORMATION AND RETRIEVAL IN RELATIONAL DATA BASES

A new framework is introduced for the treatment of incomplete information in relational data bases. The framework includes a new knowledge representation scheme for representing incomplete information in a relational data base, new kinds of data dependencies and inference rules, new definitions and realizations of relational operators for the case of incomplete information, conditions for lossless decomposition of relations containing incomplete information and results on the retrieval of information from a small version of a data base containing incomplete information. A treatment based on the operators of possibility and necessity of the system S5 of modal logic is also presented. Techniques are offered for dealing with various aspects of the information retrieval process