# Overview

A frame is a structural subsystem that acts upon another structural subsystem. Since the first tensegrities were unitary or "singleton" systems, there was no frame involved. As tensegrity research and utitilization matures, the word is used more frequently, to refer to parts of tensegrity structures in relation with other parts.

# The Duality of a Frame

"Frame" is a thought primitive with a dual aspect, derived from the same Old English source as the word "from." Just as "from" considers both an origin and destination, "frame" considers both a structural entity and the other entities that are defined by, or depend on, it. Call the first aspect "A" and the second aspect "B." A frame refers both to structural components "A" in-and-of themselves, and the relationship of this subsystem "A" to another subsystem "B" that, in being framed by "A", depends upon "A" to cohere and function. The dual nature of the word "frame" is preserved whether it is a noun or verb. As a noun, a frame is a structural system that supports other components of a physical or virtual system; as a verb, a frame is the formation, conception or activity of such a structural system that supports other components.

Consider a tetrahedron in an ordinary room formed from 6 struts connected at their nodes by glue. The six struts, in this configuration, form the tetrahedron and for all intents and purposes "are" the tetrahedron. There is no difference, conceptual or structural, between the idea of the tetrahedron or the idea of its struts, and any fact pertaining to the struts pertains as well to the tetrahedron. However, when the struts are considered as a frame, this all changes. The frame of six struts is "A", and another aspect of the tetrahedron is brought to mind. For example, the air within the tetrahedron is in a different relationship to the tetrahedron versus its frame; the air is part of the tetrahedron but not part of the frame.

This duality is obvious when considering common uses of the word "frame" in industry, such as
• A-Frame, a basic structure designed to bear a load in a lightweight economical manner, such as an A-Frame house.
• Bicycle frame, the component of a bicycle onto which other components are fitted. The same applies to a motorcycle frame, aircraft frame, etc.
• Door or window frame, a structure affixed to a building, vehicle or other container to which the hinges of doors or windows are attached.
• Space frame, a method of construction using lightweight materials.
• An HTML frame that hosts multiple HTML pages within it.
• A TCP frame, being a data transmission unit or network packet that includes frame synchronization information.

The duality is also apparent in mathematics, philosophy and other sciences, such as
• Frame of reference, a set of coordinates in which a system is observed; also a Riemannian Orthonormal frame, or a Projective geometric frame.
• Framing problems in beahvioral economics, where how a situation or price is presented affects people's behavior.