ABSTRACT
As systems continue to grow in complexity, they pose increasingly greater design and management challenges. Designing to achieve primary functional requirements is important for initial fielding of a system. Afterwards, system properties also known as ilities gain importance as a determinant of competitiveness and means to maximize the lifecycle value of systems. For example, as discussed in de Weck et al. (2011), first automobiles were motorized versions of horse-drawn carriages. Many incremental improvements were made over the long lifetime of automobiles. Initial four-wheel car brakes were replaced by hydraulic four-wheel brakes which were then replaced by dual hydraulic breaks. These changes in cars were necessary to address safety, an important system property for many engineering systems, in more demanding operating environments. Other ilities emerged over the evolution of systems. Safety, quality, reliability, usability, and maintainability are some of the core system properties that are important in any traditional engineering system including cars, airplanes, communication systems, and many more.
