When developing an information system, IS professionals follow a series of steps called a systems development life cycle (SDLC). Figure 1.1 shows a modern SDLC called the Unified Process (UP). Under the UP, an information system is built in a series of 4- to 6-week repeated steps called iterations (the vertical columns separated by dashed lines). Although Figure 1.1 shows six iterations, the number of iterations is tailored to each development projects specifications. Typically, the first iteration or two produces docu- mentation and a prototype (model) system thats refined and expanded in subsequent iterations until it becomes the final system.