Approaches for updating databases with incomplete information and nulls
Arthur M. Keller, Marianne Winslett Wilkins · 1984
In this paper we consider approaches to updating databases containing null values and incomplete information. Our approach distinguishes between modeling incompletely known worlds and modeling changes in these worlds. As an alternative to the open and closed world assumptions, we propose the modified closed world assumption. Along with the discussion of updating, we address some issues of refining incompletely specified information.