Patent US 7,849,038

A method for finding sets of two-dimensional data (S2DDs), which are similar to a target S2DD, is invented. The method leverages a new category of signatures, called equivalence signatures, to characterize the S2DDs. These signatures have the salient feature that, at worst, they change in a bounded manner when changes are made to the S2DD and when used to find S2DDs that are similar to a target S2DDs, they allow for a significant reduction in the number of SDDs to be compared with the target. This is an improvement over the state of the art wherein the computational expensive process of performing a complete search against the entire corpus must be applied.