Figure 4

Illustration of constructing a decision tree. (a) Environment. The object enclosed within the red rectangle is the target. (b) Representations of the target and sets of candidates. A GRR ($g_1^t$), color (H^t), and shape (h^t) are described as representations of the target (top row). R₁ is a set of candidates that belong to the same decomposed area$A_t^1{g}_1^t$. R₂ and R₃ are sets of candidates reduced by using the similarity criteria of color and shape, respectively (bottom row). (c) Example of a decision tree. Assume$g_1^t$and h^t are employed as nodes of the decision tree. The blue rectangle represents input to the decision tree; red rectangles represent nodes of the decision tree. The number of inputted candidates is reduced to R₁=2 by using GRR1. Then, the number of candidates (R₁) is reduced to R₁∩R₂=1 by using the shape representation.