Query Processing over Uncertain Data

An uncertain or probabilistic database is defined as a probability distribution over a set of deterministic database instances called possible worlds. In the classical deterministic setting, the query processing problem is to compute the set of tuples representing the answer of a given query on a given database. In the probabilistic setting, this problem becomes the computation of all pairs (t, p), where the tuple t is in the query answer in some random world of the input probabilistic database with probability p.