Computer Science – Databases
Scientific paper
2008-12-10
Computer Science
Databases
Scientific paper
We address the problem of finding a "best" deterministic query answer to a query over a probabilistic database. For this purpose, we propose the notion of a consensus world (or a consensus answer) which is a deterministic world (answer) that minimizes the expected distance to the possible worlds (answers). This problem can be seen as a generalization of the well-studied inconsistent information aggregation problems (e.g. rank aggregation) to probabilistic databases. We consider this problem for various types of queries including SPJ queries, \Topk queries, group-by aggregate queries, and clustering. For different distance metrics, we obtain polynomial time optimal or approximation algorithms for computing the consensus answers (or prove NP-hardness). Most of our results are for a general probabilistic database model, called {\em and/xor tree model}, which significantly generalizes previous probabilistic database models like x-tuples and block-independent disjoint models, and is of independent interest.
Deshpande Akshay
Li Jian
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