Dependency Satisfaction in Databases with Incomplete Information
Gösta Grahne · Very Large Data Bases · 1984
Two of the major problems raised by information incompleteness in databases are how to evaluate queries and how to take data dependencies into account. We give a unified solution of these two intermingled problems for the relational model. Formal criteria for the correctness of the relational algebra and dependency satisfaction are presented. We give a correct redefinition of the complete relational algebra and present a method, called a chase, for enforcing a set of functional and full join dependencies on a relation with null-values of type value exists, but is presently unknown. This novel chase can also be regarded as a generalization of previously known chase methods. The title of the paper reflects the emphasis of its contribution.