On representing indefinite and maybe information in relationaldatabases

摘要

An extension is presented of the relational model to presentnindefinite and maybe kinds of incomplete information. A data structure,ncalled an I-table, is introduced, which is capable of representingnindefinite and maybe facts. The information content of the I-table isndefined and an operator to remove redundant facts is presented. Thenrelational algebra is then extended, in a semantically correct way, tonoperate on I-tables. Queries are posed in the same way as innconventional relational algebra, but the user may expect indefinite asnwell as maybe answers