Clearly the end-user requirement for the finished product will generally be meaningless to a thrid-tier supplier, as they likely only provide a fraction of the materials for the finished product and most probably do not understand how they contribute to the end-product structure. Therefore, suppliers at each level of the process must receive the customer's demand signal and convert it to something usable (part number and quantity) to their upstream partners. From a supply chain perspective, this can be rather difficult. How can the demand signal be sent from the end customer all the way back through the supply chain?