Modeling and querying uncertain relational databases: A survey of approaches based on the possible worlds semantics
Résumé
In this paper, we give an overview of the most representative approaches aimed at querying databases containing ill-known data, starting from the pioneering works by Codd and Lipski and up to very recent proposals. This study focuses on approaches with a clear and sound semantics, based on the notion of possible worlds. Three types of queries are considered: i) those about attribute values (in an algebraic or SQL-like framework), ii) those about the properties satisfied by a given set of worlds (i.e., a set of instances of an imprecise database), and iii) those about the representation of uncertain data. For the first two types, it is emphasized that a trade-off has to be found between expressivity (of the model) and tractability (of the queries in the context of a given model).