Abstract
The evolution of database systems tends to the development of higher degree of user-friendliness such that the system can be directly handled by nonprofessionals. In order to reach this goal, the database system needs to provide a query language by which queries can be specified conceptually. Also, the query condition may be relaxed such that information within a certain semantic distance to the exact answer can be obtained. Moreover, the real-world information is usually imprecise and incomplete. It is therefore important to store imprecise and incomplete information in a database, and to manipulate this information accordingly. In this paper, we provide a conceptual query language by which fuzzy query conditions and neighborhood query conditions can be specified. Query processing strategies for these two query conditions are proposed considering imprecise and incomplete information. A domain concept hierarchy is constructed on top of a numerical domain to handle imprecise data, while dependencies between database attributes are derived for incomplete information. An application of the techniques for processing queries under network partitioning is also discussed.