automatically constructed data driven decision trees. Lin [10] also defined a
kind of motion features in his work. Many researchers used dynamic time
warping (DTW) for different extent motion sequences [1,2]. Furthermore,
there are several other methods such as probabilistic principal component
analysis (PPCA) proposed by Wang [11], movement notation language
presented by Yu et.al [12], Ensemble HMM Learning based approach
developed by Xiang and Zhu [13], energy morphing based method proposed
by Tam et.al [14] and semantic matching based method [15].