Tim Edgoose has modified Snob to allow the prior probability of the class of the next site to be derived from a first-order Markov chain sensitive to the class of the previous site. Snob itself learns the transition probabilities of the Markov chain. It is reasonable to expect the classes of neighbouring pixels to be correlated, probably positively. Edgoose's approach does not readily generalize to the 2-dimensional space of an image, unless unrealistic assumptions are made that the pixel correlations are tied to a raster scan. A more radical modification of the Snob approach is needed and is described.
Early results are encouraging.
Professor Chris Wallace received his PhD from the University of Sydney in 1959. He is a Fellow of the Association for Computing Machinery and the Australian Computer Society. His main research interests are in information theory and computer architecture. This technique is now embodied in a large computer program used by research workers in several biological and social science disciplines in Australia and overseas. Several organizations are building their own data warehouses.