In this paper we develop a My-Dragon system, in which students not only learn Chinese idioms, but also train their pet dragons through learning by demonstration. More specifically, students need to demonstrate correct procedure and answers for their dragons so that their knowledge can be improved. By doing so, students not only can be engaged in a game-based learning context, but they are offered more opportunities to master their subject domains. This is a work-in-progress study and the current status and future work are described in this paper, too.

An ordinal tree is an arbitrary rooted tree where the children of each node are ordered. Succinct representations for ordinal trees with efficient query support have been extensively studied. The best previously known result is due to Geary et al. [2004b, pages 1--10]. The number of bits required by their representation for an n -node ordinal tree T is 2 n + o ( n ), whose first-order term is information-theoretically optimal. Their representation supports a large set of O (1)-time queries on T . Based upon a balanced string of 2 n parentheses, we give an improved 2 n + o ( n )-bit representation for T . Our improvement is two-fold: First, the set of O (1)-time queries supported by our representation is a proper superset of that supported by the representation of Geary, Raman, and Raman. Second, it is also much easier for our representation to support new queries by simply adding new auxiliary strings.