Software Requirements Definition and Development Process

Abstract

This is a survey paper of various systems engineering methods used in the software requirements definition and development process. The ratio of software to hardware in aerospace systems has increased dramatically in favor of software over the last twenty years. Currently, most of the systems in aerospace vehicles are controlled by, and cannot function without, software. Studies have found that 12-13 percent of all projects are late or did not meet expectations because of incomplete or changing software requirements and specifications. This paper investigates aerospace software engineering practices, tools, literature, and research with respect to approaches to software requirements definition and analysis. It also discusses a systems engineering process that includes software development. Observations show early and thorough requirements analysis is the most cost effective and efficient means of implementing a software program. I. Introduction Aerospace systems engineering programs start with the Concept Refinement Phase, followed by Technology Development, System Development and Demonstration, Production and Deployment, and lastly the Operations and Support Phase. Within these phases the software development life cycle is embedded. This makes the design and development of software a critical part of any new or upgraded development program. The cost of repairing a software defect has been shown to increase dramatically the later it is found in the life-cycle. Technical performance parameters such as size constraints, impact on throughput performance, power required, and memory utilization are related to the systems engineering process discussed later in this paper. Observations are presented for technical directors, lead systems engineers, and software project managers to make intelligent and cost-effective decisions with respect to software requirements during software development life-cycles.