Incomplete Information in Relational Databases
Journal of the ACM (JACM)
On the representation and querying of sets of possible worlds
Selected papers of the workshop on Deductive database theory
On Databases with Incomplete Information
Journal of the ACM (JACM)
About possibilistic queries against possibilistic databases
Proceedings of the 2002 ACM symposium on Applied computing
Foundations of Databases: The Logical Level
Foundations of Databases: The Logical Level
About Possibilistic Queries and Their Evaluation
IEEE Transactions on Fuzzy Systems
Lower and upper approximations in data tables containing possibilistic information
Transactions on rough sets VII
Applying rough sets to information tables containing possibilistic values
Transactions on computational science II
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In this paper, the issue of querying databases that may contain ill-known values represented by possibility distributions is considered. The queries dealt with, called possibilistic queries, are of the form: ''to what extent is it possible that tuple t belongs to the result of query Q?'', where Q denotes a usual relational query. An evaluation method suited to these queries has been previously proposed, in the case where Q does not include any difference operation. It does not entail making explicit the different possible worlds of the database and therefore, it is possible to avoid the combinatorial growth that would be induced by a ''nai@?ve'' evaluation method. In this paper, we propose an evaluation process of possibilistic queries that makes it possible, under certain conditions, to deal with the difference operation in query Q, still without making explicit the different worlds associated with the database.