Type data bases with incomplete information

The type data base is the part of the data base in which all the information about classes, membership relationships between objects and classes and interdependencies among classes are collected. We study specific type data bases, which allow for representing different kinds of incomplete information, such as existential and disjunctive assertions. In particular, we address the problems of consistency checking and query answering, proposing efficient solutions for both of them. Our analysis is carried out in the context of the logical approach to data bases and knowledge representation, which provides a suitable formal basis for the treatment of incomplete information.