7. The method of claim 6 , wherein identifying one or more candidate clusters of observations responsive to the generated query comprises: identifying one or more candidate clusters of observations responsive to the generated query using the cluster index.
7. The method of claim 6 , wherein identifying one or more candidate clusters of observations responsive to the generated query comprises: identifying one or more candidate clusters of observations responsive to the generated query using the cluster index. 8. The method of claim 7 , wherein a respective summarized cluster for each of the one or more candidate clusters includes at least one attribute value that is included in the generated query.