31. The program storage device of claim 27, wherein the specified data includes a search template, farther comprising the steps of: said reducing comprising projecting the specified data onto a subspace for an associated cluster, based on dimensionality reduction information for the identified cluster; and generating dimensionality reduction information including an orthogonal complement for projected specified data, in response to said projecting.
31. The program storage device of claim 27, wherein the specified data includes a search template, farther comprising the steps of: said reducing comprising projecting the specified data onto a subspace for an associated cluster, based on dimensionality reduction information for the identified cluster; and generating dimensionality reduction information including an orthogonal complement for projected specified data, in response to said projecting. 32. The program storage device of claim 31, wherein said retrieving includes a nearest neighbor search, further comprising the steps of: searching the identified cluster for the k nearest neighbors to the projected specified data; determining if any other associated clusters can include any of k nearest neighbors to the projected specified data; and repeating said searching on said any clusters that can include any of the k nearest neighbors.