1. INTRODUCTION
Human motion analysis[1] is a challenging area in computer vision that includes tasks such as motion recognition and object detection. It has a wide range of applications in many fields, such as medical diagnosis, movie animation, and security inspection. Long motion sequences are usually segmented before motion analysis[2], since the segmented motion fragments contain only a single type of motion, such as running, jumping, or clapping. The segmented motion segments are further used for action synthesis[3], recognition[4], retrieval and prediction[5]. As a result, the computer vision community has devoted considerable effort to the research and development of action segmentation techniques.