A product breakdown structure (PBS) is a hierarchical chart or diagram representing a product's components or parts and their relation. It is often used in project management and product development to define the scope of work and the tasks required to complete a project.

The PBS typically starts with the final product at the highest level and then breaks it down into smaller components or lower-level subsystems. Then, each component or subsystem is further divided into more minor elements or tasks until the lowest level of detail. This breakdown helps us understand the parts needed and the required work (part of WBS).

Additionally, we know the product's associated costs, which will inform the product pricing. 

Here is an example of a product breakdown structure for a bicycle:

Figure 1.1 An example of the product breakdown for a bicycle.

As you can see, each level breaks down the product into smaller components, and each subsequent level provides more detail than the previous one. Using a PBS, project managers can better understand the product's constituent parts and relationships, which can help with planning, scheduling, and resource allocation.


Bill of Materials


A Bill of Materials (BOM) is a comprehensive list of all the components, parts, assemblies, and materials required to manufacture or assemble a particular product. It is a critical document that specifies the exact quantity, description, and cost of each item needed to build a product. In addition, it serves as a blueprint for the manufacturing or assembly process.

The BOM is in a hierarchical structure. The top level represents the finished product, and the lower levels represent the sub-assemblies, components, and raw materials required to build each level. In addition, the BOM may include additional information such as supplier names, part numbers, the unit of measure, lead times, and other relevant details.

Manufacturing, engineering, and construction industries use BOMs, where complex products or structures are built from multiple components. By having an accurate BOM, companies can ensure they have all the necessary parts and materials and accurately calculate the cost and time required to produce the product. Therefore, the BOM is critical for effective production planning, inventory management, and cost estimation.

Example of BOM

A Bill of Materials (BOM) for a bicycle could include the following components:

  1. Frame: The main structure of the bike that holds all the other components together
  2. Fork: The front part of the frame that has the front wheel and allows it to turn
  3. Handlebars: The component that the rider uses to steer the bike
  4. Stem: The part that attaches the handlebars to the fork
  5. Headset: The bearings that allow the stem and handlebars to rotate smoothly
  6. Seatpost: The component that holds the saddle (seat) in place
  7. Saddle: The seat that the rider sits on
  8. Wheels: Rims, spokes, and hubs, the wheels are what enable the bike to move
  9. Tires: The outer rubber layer of the wheels that make contact with the ground
  10. Inner Tubes: The inflatable tubes that go inside the tires
  11. Brakes: The components that allow the rider to slow down or stop the bike
  12. Brake Levers: The component that the rider uses to activate the brakes
  13. Cables: The wires that connect the brake levers to the brakes
  14. Shifters: The component that the rider uses to change gears
  15. Derailleurs: The components that move the chain from one gear to another
  16. Chain: The component that connects the pedals to the rear wheel, allowing the rider to transfer power to the bike
  17. Crankset: The component that holds the pedals and the chainrings, which determine the gear ratio
  18. Pedals: The components that the rider uses to apply force to the crankset and propel the bike forward
  19. Bottom Bracket: The component that holds the crankset in place and allows it to rotate smoothly
  20. Cassette: The gears on the rear wheel that work with the chain and derailleurs to change gears.

This BOM is just a general list as an example. The specific components (including part number and description) and their quantities may vary depending on the type of bicycle and its intended use.

Product Breakdown Structure Compared to the Bill Of Materials

A product breakdown structure (PBS) and a bill of materials (BOM) are tools used in product development and manufacturing, but they serve different purposes.
A PBS is a hierarchical chart or diagram that breaks down a product into smaller components or subsystems, with each level providing more detail on those components. The PBS defines the scope of work and tasks required to complete a project.

In addition, it helps project managers to understand better the product's components and the relationships between them, which can help with planning, scheduling, and resource allocation.
On the other hand, a BOM is a list of all the components or materials needed to manufacture a product.

It typically includes each component's part number, description, quantity, and unit cost. The BOM tracks and manages inventory and estimates the cost of producing a product.

While PBS and BOM provide information about a product's components, they serve different purposes at various product development and manufacturing stages. The PBS is used in the product planning and design phase, while the BOM is used in the manufacturing and production phases.

The PBS is a tool used to define the scope of work and tasks required to complete a project, while a BOM is used to track and manage inventory and estimate the cost of producing a product.

Manage the Product Breakdown Structure

Managing a product breakdown structure (PBS) involves keeping it up-to-date, accurately reflecting the product's components and relationships, and using it effectively to plan and execute the project. Here are some steps to manage a PBS:

  1. Update the PBS regularly: As the product development progresses, updating the PBS to reflect any changes in the product's components or relationships is essential. In addition, updating the PBS as we learn more about the product ensures that the PBS remains accurate and helpful in planning and executing the project.
  2. Use the PBS to plan and schedule tasks: The PBS can create a work breakdown structure (WBS) outlining the tasks required to complete each product component. The WBS can then plan and schedule tasks, allocate resources, and track progress.
  3. Monitor and control the project using PBS: PBS can monitor the project's progress by comparing the work completed to the planned work outlined in PBS. The PBS can help identify variances and take corrective action to keep the project on track.
  4. Use the PBS to communicate with stakeholders: The PBS can display the product's components and relationships to stakeholders such as team members, customers, and suppliers. The articulation of the product helps ensure that everyone clearly understands the product's scope and requirements.
  5. Collaborate with the team to refine the PBS: The PBS should be reviewed regularly with the team to ensure that it accurately reflects the product's components and relationships. Team collaboration can also help identify improvement areas of the PBS to support the project better.

Managing a PBS involves updating it regularly, planning and scheduling tasks, monitoring and controlling the project, communicating with stakeholders, and collaborating with the team to refine it. By effectively managing the PBS, project managers can ensure that the project stays on track and meets its goals.

Product Change Management and BOM

Product change management (PCM) manages changes to a product's design, components, or specifications throughout its lifecycle. BOMs are crucial in PCM, providing a detailed inventory of a product's components and parts.
Initiating a change to a product, whether it's a design change, a change to a component, a change in materials, or a change in supplier or product attribute, the BOM must be updated to reflect the changes. This control (via change and configuration management) ensures that the correct parts and materials are used during production and that the product functions as intended.

The PCM process typically involves the following steps:


  1. Identify the change: Determine the reason for the change and the potential impact on the product and production process.
  2. Evaluate the change: Assess the feasibility and determine the resources and actions required to implement the change. This evaluation may include additional product testing due to the change.
  3. Update the BOM: Make the necessary changes to the BOM to reflect the updated product design or component specifications.
  4. Notify stakeholders: Inform all stakeholders, including suppliers, manufacturers, and customers, about the change.
  5. Implement the change: Ensure that the updated BOM is used during production and that any relevant documentation, such as work instructions, is updated.

Effective PCM ensures that products are designed, manufactured, and delivered with consistency and quality. By maintaining accurate and up-to-date BOMs, companies can minimize errors, reduce waste, and streamline production processes.

Systems Work Together

It is a good thing for a project manager to understand the interplay of these product management systems. These product breakdowns help estimate the work, development costs, and product sales price.
From experience, changes to the product can slide under change management systems, only to find out that the new constituent part does not perform as expected in the field. The result is product rework and loss of customer trust. Therefore, we must consider these things as we design and rework the product.