Functional Hierarchy Diagram

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A Functional Hierarchy Diagram (FHD) is a visual representation used in systems engineering, project management, and other disciplines to depict the hierarchical organization of functions within a complex system, process, or project. By providing a clear and concise view of a system's functional decomposition, FHDs facilitate a better understanding of the system's structure, the relationships between its components, and the levels of abstraction involved in breaking down the system into smaller, manageable parts.

Components of an FHD:

  1. Functional Nodes: These represent specific functions or operations within the system, usually depicted as boxes or circles. Each node is labeled with a brief description of the function it represents.
  2. Hierarchical Levels: The diagram is organized in a top-down structure, with higher-level functions at the top and lower-level functions branching out below. Each level represents a level of abstraction, with higher levels being more abstract and lower levels providing more detail.
  3. Connecting Lines: Lines or arrows are used to connect functional nodes, indicating relationships and dependencies between functions and illustrating the hierarchical organization of the system's functions.

Process of creating an FHD:

  1. Define the primary function or objective: Identify the main function or goal of the system, process, or project.
  2. Decompose the primary function: Break down the primary function into smaller, more manageable sub-functions or tasks, each with a clear purpose.
  3. Create functional nodes: Represent each sub-function as a functional node in the diagram, labeling it with a brief description of the function.
  4. Organize nodes hierarchically: Arrange functional nodes in a top-down structure, with higher-level functions at the top and lower-level functions branching out below.
  5. Connect the nodes: Use lines or arrows to connect functional nodes, illustrating relationships and dependencies between them.
  6. Iterate and refine: Review the FHD and make necessary adjustments to improve clarity, accuracy, or completeness.

Importance of FHDs:

  1. Simplify complex systems or processes by visually breaking them down into a hierarchical organization of functions.
  2. Facilitate better understanding, communication, and collaboration among team members by providing a clear representation of the system's functional decomposition.
  3. Aid in identifying dependencies and relationships between components, informing the design, development, and management of the system.


Imagine a team working on a project to create a new e-commerce platform. The primary function of the platform is to facilitate online buying and selling. Using an FHD, the team would break down this primary function into smaller sub-functions, such as user registration, product listing, order processing, payment processing, and shipping management.

Each sub-function would be represented as a functional node in the diagram and organized hierarchically. The team would use lines or arrows to connect the functional nodes, illustrating the relationships and dependencies between them. This visual representation would help the team understand the overall structure and functionality of the e-commerce platform, as well as the relationships between its various components.

See Also