Hi,
Thank you for reply.
After read the article and some others like decoration, I "think" I should "hide" everything behind the main BO?

So, I would like to clarify,
If I have the BO hierarchy as following

BizItem
  |
  ---oSerial      && SerialNo. BO
  |
  ---oMatrix      && BO of Matrix (colour/size)
  |
  ---oMOutlet     && Bo which handle Item info that based on different outlet
     |
     ---oMPPU     && BO/Table which handle multi selling price, for each outlet

1. If I need to know, what is the prices available for ItemA at OutletB, where should I place the code/method, BizItem.GetPPUByOutlet() ?

2. The method above will return more than one price, and it will be stored as collection in oMPPU.oItem. Should I manipulate the collection directly by Bizitem.oMOutlet(1).oMPPU.Price? Or, BizItem should create a collection which stored the result?

3. Similar question as above, If I wan to add new price for ItemA at Outlet B, should I create a method of AddPriceByOutlet(ItemCode, OutletID) or BizItem.oMOutlet(1).oMPPU.New()?

Thank you