Radial Basis Function (RBF) networks [1][13][15] have received much attention recently because they
provide accurate generalization on a wide range of applications, yet can often be trained orders of magnitude
faster [7] than other models such as backpropagation neural networks [8] or genetic algorithms [9].
Radial basis function networks make use of a distance function to find out how different two input
vectors are (one being presented to the network and the other stored in a hidden node). This distance function
is typically designed for numeric attributes only and is inappropriate for nominal (unordered symbolic)
attributes