5. Requirements Specification
The requirements specification is a document that describes the system to be developed in a format that can be reviewed, evaluated, and approvedinasystematicway[5]. For large and complex systems in which the software component is just one of many parts, three distinct documents, depicted in Figure 4, are typically needed. These are the systems definition
document, systems requirements document, and the software requirements document [6]. In contrast, software intensive applications with no major hardware components are normally described fully in the software requirements specification.