12.2. Customer Demand and Workload
Customer demand generates workload to e-business sites. Online customers see an online store as a set of functions and services. The execution of services and functions requested by customers creates the workload processed by the site. Therefore, customer demands translate into system workload. Let us then understand why demands change in light of the reference model introduced in Chapter 1 and shown in Figure 12.1.
Figure 12.1. Revisiting the Reference Model.
As demands change, so do workloads; they may grow or shrink suddenly, depending on many factors. Demands on an e-business site vary with traffic to the site and with the functionality offered to customers. Demand expansion should be analyzed along the four layers of the reference model. Major changes in demand occur due to events that happen at the business layer. Examples of decisions or plans set at the business model layer include a new TV campaign, the launch of a new product, low price offerings, a new security policy, and special plans for events such as Christmas and Valentine's Day. At the functional layer, changes in demand are due to the introduction of new functionality and new features. For instance, demand may change when an online CD store makes available to customers a function that allows them to listen to samples of the top ten albums. If the navigation structure of a site is modified with the intent of improving customers' experience, the demand to the site may also change. For instance, the introduction of the one-click purchasing process changed customer behavior in the online stores that offered such a capability. Information technology moves fast. And so do the Web applications used by online business. New database management systems, new security software systems, new multimedia software, and new versions of operating systems are examples of software resources usually incorporated to existing sites. In general, new software systems demand additional resources from servers, disks, and networks. These new systems increase the demand at the resource level. In summary, the key to workload forecasting in e-business is understanding the nature and evolution of customers' demands.