Uncertainty models in information and database systems

Information systems have evolved to the point where it is desirable to capture the vagueness and uncertainty of data that occurs in actuality. Approaches have been taken using various fuzzy set concepts such as degree of membership, similarity relations and possibility distributions. This leads to the concept of generalized information systems which are typically char-acterized by heterogeneous data representations, weakly typed data domains and the requirement for semantic knowledge during query interpretation. A generalized information system is more likely to have a direct representation for larger classes of information at the cost of more complex data management and query processing. In general the various fuzzy database approaches that have been developed are overviewed in the paper and characterized with respect to the concept of a generalized information system