Hi Eric, Mark and Jeet, I post a blog describing the design idea of tree construction module and some works for the first week. Here is the link: http://blog.yeyanbo.com/posts/google-summer-of-code-2.html Best, Yanbo -- 叶彦波 中科院武汉病毒所生物信息学课题组 Yanbo Ye Bioinformatics Group, Wuhan Institute Of Virology, Chinese Academy of Sciences