On representing indefinite and maybe information in relational databases

An extension is presented of the relational model to present indefinite and maybe kinds of incomplete information. A data structure, called an I-table, is introduced, which is capable of representing indefinite and maybe facts. The information content of the I-table is defined and an operator to remove redundant facts is presented. The relational algebra is then extended, in a semantically correct way, to operate on I-tables. Queries are posed in the same way as in conventional relational algebra, but the user may expect indefinite as well as maybe answers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>