Consensus answers for queries over probabilistic databases

TitleConsensus answers for queries over probabilistic databases
Publication TypeConference Papers
Year of Publication2009
AuthorsLi J, Deshpande A
Conference NameProceedings of the twenty-eighth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Date Published2009///
Conference LocationNew York, NY, USA
ISBN Number978-1-60558-553-6
Keywordsconsensus answers, probabilistic and/xor tree, Probabilistic databases, Query processing, rank aggregation

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, Top-k ranking 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 and/xor tree model, which significantly generalizes previous probabilistic database models like x-tuples and block-independent disjoint models, and is of independent interest.