Hi Narendra,
Good Morning.
Ofcourse, it is possible to traverse from bottom to top. To do that we should have proper associations.
1. If you wish to traverse from leaf to root, our BOPF model will automatically taken care for the association called to_root.
2. If you wish to traverse from leaf to immediate parent, there also our BOPF model will automatically taken care for the association called to_parent.
3. If you wish to traverse for leaf to another leaf under the same branch(parent), we have to create association to traverse.
If you look into the discussion below, you will get some more clear idea.
http://scn.sap.com/thread/3664003
Regards,
Dhivya