about analysis of my project.

Question

hello sir,,

my self ashish narola from ahmd...kindly help me for my new project on Sales and inventory management system for departmental store.. but i am confuse about how can i decide the tables,flows  etc..
i am confusing about which field can i take for product_master table,sales and purchase ,account etc, i am not getting idea about it..

so. plz help

thanks
you  can take example of departmental store as Bigbazaar..or d-mart