Introduction to SAX: Adjusting Inventory
This is the state we can assume that we'd be in on an ongoing basis: The inventory table shows what we have on hand, and the products.xml file matches it.
What happens from here is going to depend on our business rules. In many cases, we will interact with our vendors to update inventory for, say incoming shipments. This may be a manual process, where an employee needs to enter the new information, or it could be an automated process, perhaps even using XML. The end result is that additional inventory is added to the totals.
The second thing that happens is that users place orders on the site. In practice, we would probably want to find a way to keep the products.xml file updated and check orders against ...