Structural decomposition:
Structures are physical components, logical objects, geometric attributes, fields, or arrangements of other structures within a design. Structures typically answer the question of "what" in a design, and typically are described using nouns and adjectives.The term structure is used to encompass not only geometry and other tangible aspects of "form", but also non-tangible entities (e.g., magnetic fields, data representations), material composition, and business organization.
Behavioral decomposition:
A behavior is an action, force, process, or control law that is exerted on or by a structure with respect to the structure's external environment. In the case that only a portion of a design (a sub design) is under consideration, other subdesigns constitute a portion of the external environment for the behavior under consideration. Behaviors typically answer the questions of "how" and "when" in a design, and are typically described using verbs and adverbs.Behaviors encompass not only data transformation and causal relationships normally associated with the word "function", but also processes, flows, and other temporal aspects of the design. In the computer field, functions often specifically exclude timing and sequencing aspects of the design; using the term behavior should help avoid confusion in that domain.