SBF[GVR] is a language for modeling physical devices. The name is an acronym for Structure–Behavior–Function, where a device is expressed in terms of its structural elements (S), the functions (F) that it manfests to its external environment, and the ways in which the structural elements collectively behave (B) to deliver those functions. Because the functions are related to the ways in which the behaviors achieve them, an SBF model of a device explains how the function is achieved. Hence, SBF serves as an explanatory framework.
An SBF Structure model describes the elements comprising a device and the connections among them. An element is either a physical component or a substance. Moreover, elements can have properties, which are named, typed values. Connections are binary, associating named connecting points within Components. Furthermore, connections are partitioned into categories based on the ways in which they transfer force.
Behavior is modeled in SBF with deterministic finite state machines (FSMs); that is, an FSM comprises a set of states and related transitions.
Functions in SBF describe the roles that elements play in the overall operation of a device. They express the purpose or goal of the element, whereas Behavior describes how the purpose is accomplished. Each component in an SBF model has a Function, and each Function has a corresponding Behavior.
In SBF, the overall functions of a device are explained by the ways in which its structural elements behave. In turn, the behavior is described by an FSM with discrete states making deterministic transitions. Moreover, each transition can be annotated with reasons why that transition is made. One of the most important such reasons is that some structural subcomponent has accomplished one of its functions. Hence, the overall functioning of a device is explained in terms of the behavior of its structural elements, which are, in turn, described in terms of the functions of those elements. In this way, an SBF model represents a device as a hierarchy of layers, each comprised of elements interacting to accomplish the device's functions. Subelements themselves are treated as devices at lower levels of abstraction. This decomposition continues until scientific laws (e.g. physics) can be used to annotate the transitions.