A fuzzy Prolog database system
A fuzzy Prolog database system
On semantic issues connected with incomplete information databases
ACM Transactions on Database Systems (TODS)
Current Approaches to Handling Imperfect Information in Data and Knowledge Bases
IEEE Transactions on Knowledge and Data Engineering
Imprecise and Uncertain Information in Databases: An Evidential Approach
Proceedings of the Eighth International Conference on Data Engineering
Handling Imperfection in Databases: A Modal Logic Approach
DEXA '97 Proceedings of the 8th International Conference on Database and Expert Systems Applications
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Data with plural sources are handled in an extended relational model under a modal logic approach. A source of information corresponds to a possible world and relationships between sources are expressed by an accessibility relation. An attribute value in a database relation is the triplet that consists of a set of possible worlds, an accessibility relation and a set of value assignment functions. A tuple in a relation consists of a tuple value and a membership attribute value to which the tuple value belongs to the relation. The degree, not always equal to 1 or 0, comes from different values being obtained from plural sources. Furthermore, the degree is expressed by two approximate values; namely, one is a degree in the lower limit that means necessity; the other is a degree in the upper limit that means possibility. This comes from sources having some relationships with others. Simple queries containing elementary formulas and logical operators are shown in the extended relational model.