Supply Chain Calcs

I have a custom inventory system that runs on PG 9.1.  I realize this is not a postgres specify question, but I respect the skills of the members of this list and was hoping for some general advice.

The system is not based on any ERP and was built from scratch.

My customer requested some supply forecasting to see when there will be a surplus or shortage of parts based on delivery dates and production dates that will require these items.

I need to identify which items will run out and when based on current available inventory, orders, delivery dates, and production dates.

Would someone please give me some keywords to google so I can track down a few different ways of doing these calculations?

Or links to any examples.  I am really not trying to reinvent the wheel here.