How to add new meta data for items & rank of feedback type ?

[ducvu91]

hello, i have many meta data for items, how to add and use it.
Another. How i can sort rank of feedback type ? ex i have read_feedback_types read and view. it mean read will greater weight than view. and it also happen with positive_feedback_types. like, add_cart can't heigher order or rating 5* after buy.
Thanks.