Hello ,
as mentioned by sander best practice is to use BX,BF and UM.
There are standard inventory cubes on which you can directly build your flow.
but suppose for ex.
there is inventory you have in BI from 01.01.2012 to 01.31.2015.
and user wants to check inventory on 31.12.2013 , in that case standard practice will not feasible, as marker update is set to 01.31.2015 and SAP done back trace calculations(which time consuming).
So, on top of inventory DS(BX,BF and UM) you need to built LSA architecture.
refer below link for implementation:
Regards,
Hitesh