“…Regarding the efficiency of hierarchical design, it has been discussed in several research articles. For example, Delgado et al proposed a multi-objective decision making scheme, allowing the evolutionary parameters based on a hierarchical genetic fuzzy system adjustable, so it not only improves the models performance (accuracy), but also guarantees the interpretability of the resulting fuzzy models (Delgado et al, 2002); Joo et al also demonstrated a scheme of hierarchical fuzzy system with constraints on the fuzzy rules approximating with high accuracy and fewer fuzzy rules (Joo and Lee, 2005); Wang proposed a hierarchical structure in a fuzzy system achieving good approximation accuracy (Wang, 1999). According to these works, it is therefore believed that improvement of inference accuracy can be achieved by use of the hierarchical design.…”