On representing indefinite and maybe information in relational databases: a generalization

The authors present a generalization of the relational model to represent indefinite and maybe kinds of incomplete information. They introduce a data structure called M-table which is capable of representing disjunctive/indefinite and maybe facts. The notion of redundancy in the context of indefinite and maybe information is studied. The information content of an M-table is precisely defined. The relational algebra is then generalized in a semantically correct manner to operate on M-tables. Queries are posed in the same manner as in the conventional relational algebra; however, the user may now expect indefinite as well as maybe answers