%0 Conference Paper
%B Proceedings of the twenty-eighth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
%D 2009
%T Consensus answers for queries over probabilistic databases
%A Li,Jian
%A Deshpande, Amol
%K consensus answers
%K probabilistic and/xor tree
%K Probabilistic databases
%K Query processing
%K rank aggregation
%X 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.
%B Proceedings of the twenty-eighth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
%S PODS '09
%I ACM
%C New York, NY, USA
%P 259 - 268
%8 2009///
%@ 978-1-60558-553-6
%G eng
%U http://doi.acm.org/10.1145/1559795.1559835
%R 10.1145/1559795.1559835