An important advantage of TClass over other techniques is that it produces comprehensible results. For instance, after combining the outputs of synthetic events from the clusterer and c4.5rules, we can produce rules that may be useful for understanding what the learner is doing.
Selected rules produced by TClass for the CBF task (see figure 2) capture some essential characteristics of each class. Because C4.5 is designed for discrimination, not characterisation, the rules should be interpreted with this in mind. For instance, it is unlikely that anything except a cylinder class will have both a maximum early in the signal and a minimum towards the end of the signal. But this does not define the cylinder class, only how it is different from the others classes.
Because matching is based on confidences, one event may actually ``register'' (i.e., produce a non-zero confidence) with multiple synthetic features. For instances, for the bell class, if there was a local maximum at time 55, it would match, with a certain confidence, the local maximum at time 48 and the local maximum at time 61. Even a maximum at time 80 would match both of these events, but with less confidence.
For the Auslan domain, selected rules found for two signs are shown against the glosses from the Auslan Dictionary [Johnston, 1989] in figure 3. Comments in square braces explain the connection between the rule and the gloss. As can be seen, some of the key characteristics of each sign are identified. For example, the identifying features for the come sign are that the hand travels far from the body (as indicated by the maximum z), there is a sudden movement of the hand away from the body early on in the sign and that the finger is initially fully bent. For the thank sign, the detected features are that there is a local maximum on channel y about midway through the sign (corresponding to the point in time where the hand touches the chin), that there is a pulling of the hand towards the body before the chin is touched, and that the forefinger remains straight for most of the sign. The comprehensibility of descriptions on both tasks is to the author's knowledge, novel. HMMs and other techniques have not been used to create comprehensible descriptions to the author's knowledge.