ENGI5003 · Professional Engineering Management
Scope, WBS, Organisation & Responsibility
Scope, WBS & Responsibility is the planning backbone of ENGI 5003: you define what a project delivers in a six-element scope statement, decompose it into a deliverable-oriented Work Breakdown Structure (WBS), then map every work package to an owner through a Responsibility Assignment Matrix (RAM/RACI). Examiners reliably test the 100% rule, the difference between a deliverable-oriented WBS and a task list, and the iron rule that each task has exactly one Accountable person — getting these right is easy marks on the closed-book exam.
What this chapter covers
- 01Project scope & the six-element scope statement
- 02Scope creep vs an approved (controlled) change
- 03Building a deliverable-oriented WBS down to work packages
- 04WBS design rules: 100% rule, mutual exclusivity, 8–80 rule, coding scheme
- 05Organisation Breakdown Structure (OBS) — who does the work
- 06Responsibility Assignment Matrix (RAM) and the RACI extension
- 07The single-Accountable rule and how to validate a RACI
- 08Apportioning a budget down the WBS (the 100% rule in dollars)
Build a WBS branch and a valid RACI
- +1List level-2 deliverables so they cover 100% of the kit: 1.1 Design, 1.2 Procurement, 1.3 Assembly, 1.4 Testing, 1.5 Project Management. These are nouns (deliverables), not verbs (actions), and are mutually exclusive.
- +1Decompose 1.1 Design into work packages: 1.1.1 Pump module, 1.1.2 PV array, 1.1.3 Controller — each a verifiable deliverable, mutually exclusive, sized roughly 8–80 hours of effort.
- +1Assign R and exactly one A per package: Project Manager = A on each; Project Engineer = R (does the work); Mechanical/Electrical designers = C on their discipline; Client = I. Example row 1.1.1 Pump module → PM:A, Eng:R, Mech:C, Elec:–, Client:I.
- +1Validate by rows: every work package has exactly one A and at least one R — no row has zero or two A's.
- +1Validate by columns: no single person is overloaded with A's (accountability is spread sensibly) and every named unit holds at least one assignment, so the matrix obeys the RAM rules.
Key terms
- Project scope
- The work that must be performed to deliver a product, service or result with the specified features and functions; in Waterfall it is fixed up front and is one leg of the cost–scope–time triple constraint.
- Scope statement
- The agreed written definition of the project boundary, carrying six elements: goal/objectives, requirements, scope description, exclusions, constraints and deliverables.
- Work Breakdown Structure (WBS)
- A hierarchical, deliverable-oriented decomposition of the total scope of work, descending from the whole project through major deliverables to work packages; it shows scope structure only, not sequence or time.
- Work package
- The lowest-level WBS element — a deliverable that one person can own and whose time, cost and resources can be reliably estimated; sized by the 8–80 rule (roughly 8 to 80 hours of effort).
- 100% rule
- A WBS design principle requiring that the children of any element sum to exactly 100% of that element's scope — nothing missing and nothing double-counted (and the elements must be mutually exclusive).
- RACI matrix
- An extended Responsibility Assignment Matrix that tags each task with Responsible (does the work), Accountable (single owner, exactly one per task), Consulted (two-way advice) and Informed (one-way notice).
Scope, WBS, Organisation & Responsibility FAQ
What is the difference between scope creep and a change request?
Scope creep is the uncontrolled, unmanaged addition of work — new features slipped in without re-baselining cost or time. A change request is legitimate change pushed through integrated change control: re-priced, re-scheduled and re-approved. The exam tests this distinction — uncontrolled = creep, controlled = change request.
Why must a WBS be deliverable-oriented and not a list of activities?
WBS elements should name verifiable noun-deliverables (e.g. 'Controller module'), not verb-actions (e.g. 'Write firmware'). Action-oriented elements break the 100% rule because you can never be sure the verbs add up to the whole result, and they pre-empt the schedule. Sequence and timing belong to the AON network and Gantt chart, not the WBS.
Why can each RACI task have only one Accountable person?
Accountability must be single and unambiguous: exactly one named owner is answerable if the task fails. Two A's means nobody is truly accountable; zero A's means the task is orphaned. Responsible (R) can be shared across many hands, but A is always one — splitting accountability is the most common planted error.
What is the difference between the WBS and the OBS?
The WBS answers what work exists (the deliverable side); the OBS, or Organisation Breakdown Structure, links that project work to the org units that will do it (the people side). Crossing the two — WBS work packages down the rows, OBS units across the columns — produces the Responsibility Assignment Matrix.
What does the 8–80 rule mean for sizing work packages?
It is a sizing heuristic, not a law: aim for work packages of roughly 8 to 80 hours of effort. Far more than ~80 hours is too coarse to estimate or control, so decompose further; far less than ~8 hours is micro-management, so roll it up. The goal is a package one person can own and estimate reliably.
Exam move
Treat this chapter as a chain — scope statement → WBS → OBS → RAM/RACI — and learn the trigger rule that gates each link. Memorise the six scope-statement elements (the one students drop is exclusions), then practise drawing a WBS that is deliverable-oriented and obeys the 100% rule, mutual exclusivity and the 8–80 rule; if a box reads like a Gantt task, rewrite it as the thing it produces. For responsibility, drill the two-pass RACI check (rows: exactly one A and ≥1 R; columns: no overload, every unit used) because examiners deliberately plant zero-A or two-A defects. Finally, remember the 100% rule reappears in money: apportioning splits a budget by % significance so children sum to the parent — fast for repeat projects, but switch to bottom-up estimation for novel ones.
