In a Function Decomposition Model , The purchasing department of Company X completes a paper purchase order and sends it to Supplier A via fax, with a copy going to the accounts payable department of X. Supplier A ships the goods and they arrive at company Xs receiving dock. A clerk at Xs receiving dock completes a paper receiving document describing the goods and sends it to Xs accounts payable department. Supplier A meanwhile sends a paper invoice to Xs accounts payable department. A clerk in Xs accounts payable department would match three documents: the original purchase order, the receiving document, and the invoice. If all three documents match, an accounts payable clerk issues a paper check to supplier A. If they dont match, an accounts payable clerk calls supplier A by phone to reconcile any shipment errors.