thanks very much. Here is what I am doing: one requirement from our customer is to mark "special" shape in part. the "special" as I know is some feature that I need to code myself. So I wish to learn this framework how to add my own feature. I have read code in package of "asiAlgo", e.g. AAG construction, how recognizer and rule works. But I am not sure if I understood them correctly. Manual document would be better like OCC.