A requirements breakdown structure (RBS) is a critical project management technique for organizing and defining the various requirements needed to complete a project successfully.
As a project manager, developing an RBS provides you with a hierarchical view of all key project requirements needed to deliver the intended product. The RBS serves as a roadmap, allowing you to group related requirements and identify dependencies logically. Though similar, it differs from a work breakdown structure which focuses on tasks.
This article will explore what an RBS is, why it’s important, how to create one properly using specific techniques, and how it differs from a WBS.
What is a Requirements Breakdown Structure?
A requirements breakdown structure (RBS) is a hierarchical representation of all the requirements needed for a project, depicted visually as a tree diagram. The RBS provides a clear outline of the requirements from top to bottom, breaking down the high-level objectives into smaller, more detailed requirements.
The RBS starts with the main project goal at the top and then branches into major categories of requirements. Each branch is then further divided into more specific functional and non-functional requirements. This top-down diagram continues decomposing until you reach detailed requirements at the lowest level.
Overall, the RBS gives you an organized understanding of the project’s requirements and their relationships. By categorizing related requirements and identifying dependencies, an RBS serves as a roadmap for what must be accomplished to deliver the final product successfully.
Importance Of the Requirements Breakdown Structure
An RBS provides critical value throughout a project’s lifecycle. Here are some of the key benefits:
1. Provides Direction
The RBS gives you a high-level view of the project’s requirements and goals. This clear roadmap helps drive tasks and schedules in the right direction for delivering the final product.
2. Organizes Complexity
Large projects can have countless complex requirements. The hierarchical RBS structure lets you categorize and group related requirements. This organization simplifies complexity, identifies dependencies, and prevents duplication of efforts.
3. Enables Collaboration
With a single RBS reference, team members have a common understanding of project requirements. This facilitates collaboration across functions. The RBS also improves communication with stakeholders by validating requirements with them.
4. Allows Traceability
The RBS enables tracking requirements back to their origin throughout the project lifecycle. This traceability ensures no scope creep and that nothing falls through the cracks.
5. Drives Progress Monitoring
As a roadmap, the RBS provides milestones to monitor progress. You can determine if project objectives are being met by validating completed requirements against the RBS which allows course correction as needed.
How to Create a Requirements Breakdown Structure
Creating an effective RBS takes time and thought. Follow these key steps:
1. Gather Requirements
First, work with stakeholders to gather all known project requirements and compile them into a master list. These requirements can come from documents, interviews, surveys, etc.
2. Identify Categories
Next, study the requirements to identify logical groupings and categories. Common ways to categorize include:
- By component (frontend, backend, infrastructure)
- By process (workflows required)
- By stakeholder type (sales, customer, accounting)
- By priority (critical, high, medium, low)
Choose intuitive categories that make sense for your project.
3. Map the Structure
Now map out the RBS structure starting with the main project goal. Break this down into major categories, then divide further into smaller sub-requirements. Keep decomposing until you reach very specific requirements.
4. Add Details
With the structure in place, go through each low-level requirement to add details like ID codes, priority, owner, and status.
5. Validate with Stakeholders
It’s critical to review the RBS with stakeholders and get their sign-off. This validates completeness and shared understanding.
6. Manage Changes
The RBS is a living document. As requirements change, update the RBS and validate again with stakeholders. Use RBS traceability to manage changes.
Requirement Breakdown Techniques
Creating an effective RBS takes thoughtful technique. Use these tips when building your RBS:
1. Ask “Why?”
For each requirement, ask “Why is this needed?” to unpack the reasoning. This helps create detailed sub-requirements. If a stakeholder needs purchase tracking, ask why to uncover needs like order history, refund processing, and customer profiles.
2. Avoid Ambiguity
Requirements should be objective, unambiguous, and verifiable. Avoid vague terms like “easy”, “improved”, or “robust”. Instead, use concrete details like response time under 2 seconds.
3. Prioritize
Work with stakeholders to assign priorities such to high, medium, or low. This highlights what’s critical versus what’s merely nice-to-have. Then focus energy on the high-priority requirements.
4. Visualize
A picture says a thousand words and using a visual diagram makes the RBS relationships clear. Use a tree structure, indenting subordinate requirements under parents.
5. Collaborate
Schedule collaborative workshops to build the RBS to ensure stakeholder alignment and shared understanding from the start.
6. Validate Completeness
Validate that the RBS is comprehensive by double-checking that all stakeholder needs that were identified upfront are captured somewhere in the RBS.
Requirements Breakdown Structure Example
Let’s look at an RBS example for a website redesign project:
The main goal is to redesign the company website. The major categories of requirements are Content, Functionality, and Performance.
The Content branch breaks down into sub-requirements like text, images, videos, and blog posts.
The Functionality branch details needs like responsive design, integrated e-commerce, account registration, and search capabilities.
Finally, the Performance branch captures non-functional requirements like page load speed under 2 secs, 99.9% uptime, and mobile optimization.
This simplified example demonstrates how an RBS decomposes a project goal into organized categories and increasing levels of detail. The RBS provides a clear roadmap of all requirements needed to deliver the website redesign successfully.
Requirements Breakdown Structure vs Work Breakdown Structure
Though similar in using a hierarchical structure, the RBS and WBS serve different purposes.
1. Requirements vs Tasks
The RBS focuses on defining the requirements needed for project success. In contrast, the WBS outlines discrete tasks required to deliver the product. The RBS is about the “what” while the WBS details the “how”.
2. Waterfall Dependence
An RBS often comes before and feeds the WBS in waterfall projects. The WBS tasks should map to realizing RBS requirements. This dependency is less common in Agile projects.
3. Shift Over Time
The RBS is more static with few changes over the project lifecycle, while the WBS evolves over time as tasks are completed and new work packages are added.
4. Stakeholder Input
The RBS requires heavy stakeholder input to gather and define requirements. In contrast, stakeholders are less involved in building the task-driven WBS.
5. Project Understanding
An RBS provides a view of the project end goals while the granular WBS better enables estimation, scheduling, and resource planning.
Final Thoughts
A requirements breakdown structure (RBS) is a critical technique for organizing complex projects. Developing an RBS provides immense value by mapping out all key requirements in a hierarchical structure. It gives direction, enables collaboration, allows traceability, and drives progress monitoring. While requiring upfront effort, the clarity and shared understanding an RBS provides pays dividends throughout the project lifecycle, increasing the likelihood of delivering the right product successfully. For any complex project, investing time in developing a thoughtful RBS aligned to stakeholder needs is a must.
