When a product is used or shared by multiple individuals, integrates with many other physical and non-physical elements, and is sufficiently complex and expensive to develop, it moves into the domain of systems design. These systems will have numerous stakeholders and decision makers with varied and multiple competing objectives.
These objectives must be traded across the vast number of dimensions and perspectives including design and engineering variables, operational and logistic parameters, economic factors, and the socio-techno-political demands of society. The definition, analysis, and exploration of the interfaces or interrelationships of two or more disciplines are always part of good systems design.
Since multiple concepts and solutions can exist to meet the requirements, gradient-free optimization and satisficing strategies are often employed for the multi-objective decision-making processes. Systems are often too complex for full-scale testing and rely upon computer-aided design and virtual testing and evaluation through, for example, agent-based modeling, discrete event simulation, and system dynamics. Examples of systems include, but are not limited to, the design of an airport, alternative energy systems, autonomous vehicles, space systems, and cooperating swarms of UAVs.