We defined a “system” as any organized collection of discrete elements (e.g., parts, processes, people) designed to work together in interdependent ways to fulfill one or more functions. Our analysis suggests that systems and systems thinking are fragments of thread interwoven with other, more continuous threads. By this, we meant that systems and systems thinking do not permeate any single curriculum. Both concepts are used selectively, often to help students analyze or explain how a technology works.

The committee’s definition of systems is consistent with the definitions in the curricular materials that addressed systems in some manner. For example, “City Technology” explained systems as “a collection of interconnected parts functioning together in a way that make the whole greater than the sum of its parts.” In “Engineering is Elementary,” a system is defined as “a group of parts that interact to create a product”; in one unit it is defined as “a group of steps that interact to create a process.” In the Models and Designs unit of the “Full Option Science Systems” curriculum, system is defined as “two or more objects that work together in a meaningful way.”

The concept of systems is treated most directly in curriculum initiatives focused on domain knowledge. In these cases, systems thinking is often an undercurrent in the storyline of how a specific technology works. The same is true in “The Infinity Project for Middle School,” which stresses that most technological systems follow a pattern of inputs, processes, and outputs. The materials provide illustrations of sophisticated systems in the form of simple flow charts that accompany explanations in the text of how the systems work; the illustrations are also organizers for laboratory activities related to such things as digital music, digital images, and data encryption.

The “Engineering is Elementary” and “Design and Discovery” curricula introduce the idea that systems can be divided into subsystems and that subsystems can be further divided into components. In the “Design and Discovery” curriculum, a laboratory activity is focused on analyzing bicycles in terms of systems, subsystems, components, and parts.

Several curricula featured units or lessons in which reverse engineering is used to engage students in studying simple devices from a systems perspective. These activities involve identifying parts, determining their function, uncovering relationships, discovering how they work together as a system, and identifying ways to improve their performance. This kind of systems thinking was the part of lessons in the “City Technology,” “Design and Discovery,” and “Designing for Tomorrow” curricula that ultimately engaged students in exploring opportunities for redesigning products.