ABSTRACT
In Chapter 3, we learned everything about requirements, including what system requirements are, how to write good requirements, where to obtain them, and how to manage them. Requirements define the system, but they cannot design the system. Requirements tell us what is desired for the system, but will not tell us how to make it happen. In other words, requirements are design independent; that is to say, the details to achieve those requirements are yet to be determined and there may be more than one way to fulfill those needs. Systems engineering uses requirements to drive the design in the right direction, but the use of a well-structured design process and a series of methods, models, and activities, leading to the final form of the system, bring it into being. System requirements need to be translated into technical specifications. This process of translation requires designers to have the necessary knowledge of the nature of the system and use appropriate models at the right time. When designing systems, especially complex ones, there are hundreds of thousands of factors and variables involved. It is nearly impossible to study the relationships of these factors to the design without using some kind of model. As the representation of the system, models are essential for designers to concentrate on the most critical factors of the design, simplifying the situation by ignoring the nonrelevant factors, and thus enabling them to provide a solution for the problem to be addressed. This chapter is intended to review the most commonly used models for system design once the requirements are developed; these models, although we call them systems engineering design models, are by no means solely developed for systems engineering. There are no such things as systems engineering models; systems engineering uses any models that are deemed useful for design purposes. As systems engineering is a relatively new discipline, it is an applied field; most of the models utilized in the field of systems engineering are borrowed from other fields, such as social studies, psychology, and operations research/simulation, to name a few. In this chapter, we will attempt to give a comprehensive review of some of the models that may be used in systems design; more specifically,
1. Define models, review the benefits of using models and categorize models.
