As shown in Figure 3, an SCM model may be constructed via the “mass balance equations” approach to systems engineering advocated by Parnaby[13]. Thus, supply chain customer/supplier relationships have to be viewed as concerning material flows, information flows, and cash flows both within and between businesses[14]. Moreover, these flows are time-varying and need to be controlled holistically if supply chain operation is to be stable and effective. If a supplier fails to deliver, the customer loses time as well as money and is unlikely to recover on either score.