It is difficult to pinpoint when the discipline of systems engineering began. Different sources cite different dates and attribute the term to different persons or organizations. The discipline and the term began gaining broader acceptance sometime in the late 1940s or early 1950s. However, the principles of systems engineering were being practiced long before the discipline was formalized. In fact, it has been said that systems engineering is just doing what good engineers do. Of course, that does not help those who are trying to learn how to become good engineers. Before trying to discuss the principles and processes of systems engineering, a definition of both a system and systems engineering should be established. In our context, a system is defined as two or more components interacting together to achieve a common objective. Finding a concise definition for systems engineering that captures the breadth of systems engineering is not easy. Combining several accepted definitions, including those in Chapter 1, systems engineering is basically an interdisciplinary approach to realize a system, which meets the customer’s needs and considers

operations, performance, manufacturing, test, cost and schedule, support and maintenance, and disposal throughout design and development. Despite the many definitions of systems engineering, there are some fundamental properties that are common. These are

• Develop requirements based on customer or user needs. It may be the case that the customer or user may not fully understand what is needed or know what is achievable. Part of systems engineering is to work with the customer to gain this understanding and translate it into system requirements. It is important to focus on what is needed before determining how to realize it. Determine the what before the how.