From the pdf: A central concern of systems engineering is selecting the most preferred alternatives for implementation from among competing options. The selection process is sometimes called tradeoff analysis, and is often built on the methods of decision analysis and utility theory. The process can be loosely divided into two parts, a first part in which one determines the relative priority of various requirements, and a second part, a design selection phase, in which alternatives are compared, and the preferred alternatives chosen. This paper discusses the means of determining the priority order for implementing system changes. It also outlines the implications on the selection process of evolutionary systems development.