Merits and Drawbacks of Development Methodologies

1.2.3 Software development · Paper 1 · 5 flashcards · 4 questions

Waterfall

Pros & Cons

Pros & Cons:

Advantages	Disadvantages
Clear structure and milestones	Inflexible - hard to change requirements later
Easy to understand and manage	No working software until late in process
Comprehensive documentation	High risk if requirements misunderstood
Works well for fixed-requirement projects	Poor for complex or innovative projects

Best when: Requirements are fixed and well-understood, safety-critical systems

Agile

Pros & Cons

Pros & Cons:

Advantages	Disadvantages
Flexible - welcomes changing requirements	Less predictable timeline and cost
Working software delivered frequently	Requires high customer involvement
Close customer collaboration	Can lead to scope creep
Quick response to feedback	Documentation may be insufficient

Best when: Requirements likely to change, innovative projects, customer available

Extreme Programming

Pros & Cons

Pros & Cons:

Advantages	Disadvantages
High code quality through practices like TDD	Requires experienced developers
Continuous feedback and improvement	Pair programming costly (two salaries)
Knowledge sharing through pair programming	Customer must be on-site
Low defect rates	Difficult to scale to large teams

Best when: Small expert teams, quality-critical projects, volatile requirements

Spiral

Pros & Cons

Pros & Cons:

Advantages	Disadvantages
Systematic risk management	Complex to manage
Early detection of problems	Expensive - extensive planning and risk analysis
Flexible - can accommodate changes	Not suitable for small projects
Suitable for large, complex projects	Requires expertise in risk assessment

Best when: Large, complex, high-risk projects (banking, defence)

RAD

Pros & Cons

Pros & Cons:

Advantages	Disadvantages
Very fast delivery	Requires modularity
High user satisfaction through involvement	Heavy dependence on user availability
Reduces requirements errors	Not suitable for complex, low-modularity systems
Efficient for well-understood problems	May sacrifice quality for speed

Best when: Tight deadlines, available users, modular architecture, clear scope

Exam questions on Merits and Drawbacks

1 OCR past paper question and 3 practice questions (22 marks) with mark schemes

Question 1H446/01 · June 20229 marks
A programmer has been asked by a client to create a complex computer program. Compare the spiral model and waterfall lifecycle methodologies for this task. You should include: how both methodologies could be used to develop a complex computer program, the benefits of each methodology for this task, the drawbacks of each methodology for this task.
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Levels of response question (9 marks) AO1: The spiral model has four quadrants (determine objectives, identify and manage risk, develop and test, plan next iteration). Client feedback informs future development and prototypes. Waterfall has structured analysis/design/development/test flow. Progress to next step only after previous step completed. AO2: Spiral model relies on frequent client feedback, produces functional prototypes where features are added incrementally. More focus on risk; projects may be modified or dropped if risk too great. Waterfall is more structured and reliant on getting requirements correct at start; changes harder to add later. Forces definition to be well understood. AO3: Spiral involves client feedback, prototypes and evolving projects - better where requirements may change. Waterfall better where requirements are clear and outcomes known. Spiral better for risk management. Waterfall may be more appropriate with large teams due to clearly defined responsibilities.
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Question 2Practice question · H446/01 style4 marks
A small company wants a stock-control system. Its requirements have been fully documented and are unlikely to change. Explain why the waterfall lifecycle is suitable for this project and describe one drawback of using it.
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Suitable because: • Requirements are fixed / well understood, so each stage can be completed in order • Clear milestones and documentation make progress easy to plan and manage Drawback (any one, described): • Testing happens late, so errors found late are expensive to fix • The customer sees no working software until the end • Difficult / costly to go back and change requirements once a stage is complete (4 marks – max 2 for suitability, max 2 for a described drawback)
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Question 3Practice question · H446/01 style6 marks
A games studio is developing a new game and expects the requirements to change frequently as players test early versions. Compare rapid application development (RAD) and the waterfall lifecycle for this project, and recommend which the studio should use.
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RAD: • A prototype is built quickly and shown to users / players • Feedback is used to refine the next iteration • Suits projects where requirements change Waterfall: • Sequential stages, each completed before the next begins • Requirements are fixed at the start, so changes are difficult / expensive • No working version until late in the project Recommendation: RAD, because the requirements will change and player feedback is central to the design (1 mark for a justified recommendation) (6 marks – max 3 for RAD, max 3 for waterfall, including the recommendation)
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Question 4Practice question · H446/01 style3 marks
Explain why the spiral model is suited to large projects where the risks are not fully understood at the start.
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• Each loop / iteration begins by identifying and analysing risks • Risks can be reduced (e.g. by prototyping) before more time and money are committed • The project can be changed or abandoned at any loop if the risk is too high • Repeated cycles let the plan be refined as understanding of the problem improves (3 marks – 1 per point, max 3)
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