A Model Based on Possibilistic Certainty Levels for Incomplete Databases

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This paper deals with the modeling and querying of a database containing uncertain attribute values, in the situation where some knowledge is available about the more or less certain value (or disjunction of values) that a given attribute in a given tuple can take. This is represented in the setting of possibility theory. A relational database model suited to this context is introduced, and selection, join and union operators of relational algebra are extended so as to handle such relations. It is shown that i) the model in question is a strong representation system for the algebraic operators considered, and that ii) the data complexity associated with the extended operators in this context is the same as in the classical database case, which makes the approach highly scalable. A possibilistic logic encoding of the model is also outlined.