U Uncertain Data Lineage

Lineage, also called Boolean provenance, event expression, or why-provenance, is a form of provenance or origin of the answer(s) to a query executed on a database. Lineage is expressed as a Boolean formula with variables assigned to the tuples in the database, where joint usage of the tuples (by the database join operation) is captured by Boolean conjunction (AND, ^) and alternative usage (projection or union) by Boolean disjunction (OR, _). Uncertain data is typically expressed in the form of a probabilistic database, which is a compact representation of a probability distribution over a set of deterministic database instances (called possible worlds). When an input query is evaluated on such a probabilistic database, instead of a deterministic set of tuples representing the answer, the output is a distribution on possible answers for the possible worlds. The query evaluation problem on uncertain data aims to compute this output probability distribution efficiently. Lineages of the answers play a key role in understanding, expressing, and efficiently evaluating the probability distribution of query answers for uncertain data.