Ch7. Agile vs. Waterfall — Choosing the Right Methodology

The Fundamental Difference

Waterfall:
Requirements → Design → Development → Testing → Deployment
→ Sequential: each phase must be complete before the next begins
→ Cost of change = very high
→ Best when requirements are clear and unlikely to change

Agile:
Short iterations (sprints) → Review and feedback → Next iteration
→ Parallel and iterative
→ Cost of change = low (flexibility is a design goal)
→ Best when requirements are unclear or frequently changing

The Agile Manifesto (2001)

Four core values:
Individuals and interactions  OVER  processes and tools
Working software              OVER  comprehensive documentation
Customer collaboration         OVER  contract negotiation
Responding to change           OVER  following a plan

→ "The items on the right have value,
   but we value the items on the left more"

Scrum — The Most Widely Used Agile Framework

Roles

Product Owner:
→ Prioritizes the product backlog
→ Responsible for maximizing business value

Scrum Master:
→ Coaches the Scrum process
→ Removes impediments (Servant Leader)
→ A facilitator, not a project manager

Development Team:
→ 5–9 people, self-organizing
→ Collectively responsible for achieving the sprint goal

Events

Sprint:       1–4 week iteration (commonly 2 weeks)
Sprint Planning:  Select work at the start of each sprint
Daily Scrum:  15-minute standup
  → What I did yesterday / What I'll do today / Any blockers
Sprint Review: Demonstrate the increment to stakeholders
Sprint Retrospective: Team discussion on process improvement

Artifacts

Product Backlog:   Prioritized list of all product requirements
Sprint Backlog:    Work items selected for the current sprint
Burndown Chart:    Visual of remaining work over time
Increment:         The working product built each sprint

Kanban

Principles:
- Visualize the workflow (To Do → In Progress → Done)
- Set WIP (Work in Progress) limits
- Manage flow → identify and remove bottlenecks

Difference from Scrum:
Scrum: uses time-boxed sprints
Kanban: flow-based, no time boxes

Best suited for:
→ Operations and maintenance work
→ Teams with continuous incoming requests
→ IT help desks, marketing teams, support teams

How to Choose a Methodology

Factor	Waterfall	Agile
Requirements	Clear and fixed	Unclear or changing
Customer involvement	Front-end and end	Continuous
Team size	Can scale large	Small teams preferred
Risk profile	Front-loaded	Distributed across iterations
Regulatory environment	Heavily regulated (healthcare, finance)	Flexible environments
Delivery model	Single final delivery	Incremental releases

Hybrid Approaches

The practical reality:
→ Pure Waterfall or pure Agile is less common than hybrid

A typical hybrid example:
- Planning & design = Waterfall
- Development & testing = Agile sprints
- Deployment & operations = Kanban

SAFe (Scaled Agile Framework):
→ Extends Agile across large enterprises
→ Team → Program → Portfolio levels
→ Organized around Agile Release Trains (ARTs)

Waterfall: sequential execution after requirements are locked — high cost of change Agile: iterative and incremental — driven by customer feedback Scrum roles: Product Owner, Scrum Master, Development Team Scrum events: Sprint, Sprint Planning, Daily Scrum, Sprint Review, Sprint Retrospective Methodology selection: clarity of requirements + frequency of change + regulatory environment