26. A program storage device readable by a machine which includes one or more reduced dimensionality indexes to multidimensional data, the program storage device tangibly embodying a program of instructions executable by the machine to perform method steps for representing multidimensional data, said method steps comprising: a) partitioning the multidimensional data into one or more clusters; b) generating and storing clustering information for said one or more clusters; c) generating one or more reduced dimensionality clusters and dimensionality reduction information for said one or more clusters; and d) storing the dimensionality reduction information; e) creating a hierarchy of reduced dimensionality clusters by recursively applying said steps a) through d); and f) generating and storing one or more low-dimensional indexes for clusters at a lowest level of said hierarchy.
26. A program storage device readable by a machine which includes one or more reduced dimensionality indexes to multidimensional data, the program storage device tangibly embodying a program of instructions executable by the machine to perform method steps for representing multidimensional data, said method steps comprising: a) partitioning the multidimensional data into one or more clusters; b) generating and storing clustering information for said one or more clusters; c) generating one or more reduced dimensionality clusters and dimensionality reduction information for said one or more clusters; and d) storing the dimensionality reduction information; e) creating a hierarchy of reduced dimensionality clusters by recursively applying said steps a) through d); and f) generating and storing one or more low-dimensional indexes for clusters at a lowest level of said hierarchy. 41. The program storage device of claim 26, for performing an exact search, comprising the steps of: associating specified data to one of the clusters based on stored clustering information; reducing the dimensionality of the specified data based on stored dimensionality reduction information for a reduced dimensionality version of a cluster, in response to said associating step; and searching, based on reduced dimensionality specified data, for the reduced dimensionality version of the cluster matching the specified data.