On the treatment of imperfect information in intelligent databases

A relational data model is extended under a modal logic approach so that it can deal with different kinds of imperfect information. In the extended model the imperfect information is uniformly represented in a set of possible worlds and an accessibility relation. This leads to the extended data model having the same operations to different kinds of imperfect information. Moreover, the model can support flexible queries. The approach gives fundamentals to integrate different kinds of databases handling different types of imperfect information.