What is the significance of the dragon king in Dragonwings by Laurence Yep?

In Chapter Two, Moon Shadow learns of his father's dream that he was once a dragon and must prove himself as a human in order to earn the right to become a dragon again. The Tang people hold dragons in great esteem and this dream goes toward the traditions and the beliefs of the Tang people. This dream also defines the way in which Windrider intends to live his life and his own dream of once again flying like he did in the dream. It is this latter dream that will inspire and motivate these characters in a large portion of the novel.