How to do multi-way classification with two-way classifiers

Abstract

A new principle for performing polychotomous classification with pairwise classifiers is introduced: if pairwise classifier Nij, trained to discriminate between classes i and j, responds "i" for an input x from an unknown class (not necessarily i or j), one can at best conclude that x ∉ j. Thus, the output of pairwise classifier Nij can be interpreted as a vote against the losing class j, and not, as existing methods propose, as a vote for the winning class i. Both a discrete and a continuous classification model derived from this principle are introduced. © Springer-Verlag Berlin Heidelberg 2003.