23.5.2 Decision Boundary Uncertainty
In Decision Boundary-based methods, training points are selected so as to improve
decision boundaries. Often an existing decision boundary is assumed to be somewhat accurate, so points are sampled close to the decision boundary to further refine
it (Figure 23.4). In a way this may also be considered Output Uncertainty-based,
since the uncertainty of the points close to the decision boundary may be high. This
method operates with the assumption that the decision boundary of the underlying
learning method (e.g. Support Vector Machine) is easily accessible. A clear advantage of this method is that given a decision boundary, selecting training examples
by their proximity to it is computationally inexpensive.