approaches to handling imperfect information in data and knowledge bases

This paper surveys methods for representing and reasoning with imper-fect information. It opens with an attempt to classify the dierent types of imperfection that may pervade data, and a discussion of the sources of such imperfections. The classication is then used as a framework for considering work that explicitly concerns the representation of imperfect information, and related work on how imperfect information may be used as a basis for reasoning. The work that is surveyed is drawn from both the eld of databases and the eld of articial intelligence. Both of these areas have long been concerned with the problems caused by imperfect infor-mation, and this paper stresses the relationships between the approaches developed in each.