Although many life-cycle models emphasize the requirements phase as an upfront activity, it is actually an iterative one that continues throughout the entire lifetime of the project [3,4]. Requirements drive not only the initial design and validation of the system
support ongoing activities such as change management, regression test selection, and compliance monitoring. The requirements process can be described by the five primary disciplines of requirements elicitation, analysis, specification, validation, and management. Although there is overlap between these activities they are described here as individual phases for pedagogical purposes.