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Representing Requirements Hierarchy Diagram

The hierarchy diagram – one of the oldest and most used systems engineering graphical views – represents relationships between several layers or types of elements. There is no pre-defined semantic for a hierarchy, allowing the creator to define the specific set of relationships to deliver the desired representation and insight. Sample uses include representing requirements hierarchies as well as functional composition, physical composition, and traceability across the design.

Level of Detail: Low Audience: General Content: Names and relationships Use: Multi-level decomposition of requirements

A hierarchy diagram is based on the combination of a root element and a set of relationships to display. The root element defines the starting point for the diagram and is classically shown as a node on the top (in a top-down representation) or left (in a left-to-right representation). Individual elements are shown as nodes with the relationships between the elements shown as connecting lines. Classically, the information content is kept to a minimum with nodes showing element names and perhaps number, type, or class (although any information can be displayed, as desired). The emphasis in a hierarchy diagram is on interrelationships, with connecting lines frequently labeled to clearly communicate the nature of the relationship between the elements unless the diagram only shows composition (a pure hierarchy of requirements, functions, or components).

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