من قبل
Zaid Rabab'a , Software Development Team Leader , Al-Safa Co. Ltd.
use existing programs that may helps
OpenERP but i think its not free you need 33 USD per user/month
or check this http://ofbiz.apache.org/ , its totally free
I think that depends on the need of the institutions because there are different major factors that should be taken into consideration .
1) costing method such as FIFO, weight method
2) the cycle of PO and SO
3) the item types like items, serial, batch
4) some institutions use dissassembly and assembly for the inventory module
5) the financial integration with other modules
the above points are a small sample of the major factors because the industry of each institutions plays a major role to define "what i really need"
for example, in medicine industry they need to use batches for the items because they have expiry dates but in furniture fields they use serials and they don't care about the expiry dates
You can depend on any existing open source ERP and adapt it and customize it for your needs rather than starting from scratch, there is a wide variety of open source ERPs:
OpenERP
Openbravo
Apache OFBiz
and many others.