HKSM

A hierarchical view of all resources needed for the project, grouped by category and type. It helps plan, estimate, acquire, and control both human and non-human resources.

Key Points

• An RBS is a hierarchical decomposition of resources (people, equipment, materials, facilities, and services).
• It is organized by category and type, not by deliverables or organizational units.
• Supports planning, estimating, budgeting, risk identification, and procurement alignment.
• Helps avoid double-counting by clarifying unique resource types and ownership.
• Enables traceability by assigning resource codes and mapping to the WBS or RAM.
• Should be tailored to the project and kept under change control as needs evolve.

Purpose of Analysis

The RBS provides a clear structure for understanding what resources are needed and how they group together, so the team can plan staffing, procurement, logistics, and costs. It also highlights gaps, overlaps, and key constraints early, improving estimates and decisions.

Method Steps

• Define top-level categories (e.g., human resources, equipment, materials, facilities, services).
• Tailor the taxonomy to the project (e.g., by skill family, equipment class, material type, supplier).
• Gather inputs: scope, WBS, resource requirements, org data, historical information, and procurement strategy.
• Decompose each category into types and subtypes until useful for estimating and acquisition.
• Assign a coding scheme (e.g., 1.2.3) for traceability and reporting.
• Validate with stakeholders (functional managers, procurement, finance) and refine.
• Baseline or version-control the RBS and integrate with the resource management plan.
• Maintain the RBS as changes occur and align it with the schedule and cost structures.

Inputs Needed

• Project scope statement and WBS.
• Resource management plan or strategy.
• Initial activity list and resource requirements.
• Organizational charts, skills inventory, and role definitions.
• Procurement strategy, make-or-buy decisions, and supplier catalogs.
• Historical data, lessons learned, and organizational process assets.
• Budget categories and cost account structure.

Outputs Produced

• RBS diagram with hierarchical codes.
• Resource dictionary describing types, attributes, and assumptions.
• Updated resource requirements and estimates by resource type.
• Staffing profiles and procurement item lists aligned to categories.
• Inputs to risk register (e.g., scarce skills, single-source items).
• Mappings to WBS and responsibility assignment matrix (RAM) for traceability.

Interpretation Tips

• Read from top to bottom: higher levels are broad categories; lower levels are specific types.
• Check completeness by sampling WBS work packages and ensuring required resources appear in the RBS.
• Watch for overlaps where the same resource type appears in multiple branches.
• Use codes to link RBS entries to estimates, calendars, and cost accounts.
• Align RBS categories with procurement and finance labels to simplify reporting.

Example

A simple RBS for a project might look like this:

• 1. Human resources: project manager, business analyst, developer, tester, trainer.
• 2. Equipment: laptops, servers, networking gear, specialized tools.
• 3. Materials: consumables, spare parts, office supplies.
• 4. Facilities: meeting rooms, lab space, staging area.
• 5. Services: cloud hosting, external consulting, training services, logistics.

Pitfalls

• Confusing RBS with WBS or OBS and mixing deliverables or departments into the resource structure.
• Too much detail that becomes unmanageable and does not improve estimates.
• Too little detail that hides key constraints or cost drivers.
• Ignoring non-labor resources such as services, facilities, and materials.
• Inconsistent naming and coding that break traceability to estimates and costs.
• Not updating the RBS as scope, schedule, or procurement decisions change.

PMP Example Question

A project manager wants to improve resource estimating and procurement planning. Which tool should they use to categorize all resources by type and ensure nothing is missed?

1. Work breakdown structure (WBS).
2. Organizational breakdown structure (OBS).
3. Resource breakdown structure (RBS).
4. Responsibility assignment matrix (RAM).

Correct Answer: C — Resource breakdown structure (RBS).

Explanation: The RBS groups all resource types hierarchically, aiding estimating and procurement. WBS is about deliverables, OBS about organization, and RAM maps responsibility to work.