Benchmark 11A
Common Themes: Systems
Grades 9-12, page 266

Understanding how things work and designing solutions to problems of almost any kind can be facilitated by systems analysis. In defining a system, it is important to specify its boundaries and subsystems, indicate its relation to other systems, and identify what its input and its output are expected to be.

See the general discussion in Unifying Concepts and Processes: Systems, order, and organization