A FAST IMPLEMENTATION OF A PERFECT HASH FUNCTION FOR PICTURE OBJECTS

In image database systems, symbolic pictures are represented by two-dimensional (2D) strings that are converted into triples. Each triple is mapped to a unique hash address for timely retrieval of pictures, reducing the pattern-matching problem corresponding to a query to that of computation of a hash function. The values associated with the picture objects are used to compute hash addresses for triples developed from the query. Heuristics are proposed to speed up the computation of the associated values for the picture objects. Experimental results show that the new algorithm achieves almost a 90%. gain, in search space, over existing algorithms to compute the associated values.