Abstract: A computer control program directs a method whereby a computer reads a data entry record group from a data stream, wherein the data entry record group comprises one or more data entry records containing a key field containing an item. A key number representing the total number of key fields in the data entry record group is tallied, and a marker that allows for locating, and determining the size of, the data entry record group within the stream of data is recorded. The computer converts each item of the data entry record group to fixed length coded equivalence called an item indicator, and converts the item indicators to a fixed length coded equivalence called a signature. The computer creates a partial index record for each signature, and updates a combination cross-reference file and a raw data index, thereby classifying the data to allow for subsequent searching by persistent fast search methods.

Abstract: A method for identifying fingerprints is disclosed; the method produces a descriptor code which is uniquely related to a given fingerprint impression. A fingerprint pattern is transformed into an informational model which represents the relative location of all data points with respect to selected groups of other data points. The method comprises the steps of transforming the fingerprint impression into a representation of a three-dimensional surface wherein the Z-axis coordinate has a value dependent upon the frequency of occurrence of ridge lines at a specific set of X-axis and Y-axis coordinates when the origin is taken at multiple positions over a prescribed part of the fingerprint impression, determining the values of local spatial derivatives, such as the surface curvature of a plurality of different areas of the three-dimensional surface, and concatenating the values in a predetermined order to construct a descriptor code for the fingerprint.