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OCR H446 1.2.3 Waterfall lifecycle and spiral model

Part 1 of 6 · H446 1.2.3 · Software development

H446 1.2.3 asks not what waterfall and spiral are called but what their movement changes for a project. This worksheet traces a linear route and a risk-driven cycle against contrasting briefs, so iteration, risk and change are argued as consequences rather than as labels.

Students will:

  • follow the stages of a waterfall lifecycle and the repeating structure of a spiral cycle
  • explain a benefit and a drawback of waterfall for a project with fixed, signed-off rules
  • design a first spiral cycle with an objective, a major risk and a risk-reduction activity
  • explain how evidence from one cycle changes the plan for the next
  • compare both routes for a project carrying safety and integration risk, then recommend one

Inside: 6 explanation cells, 1 multiple-choice question, 2 fill-in-the-blanks cells and 4 written answers. 36 marks, about 45 to 55 minutes.

Series: H446 1.2.3 · Software development, part 1 of 6.

Shared by Coding PathwayVerified teacher

  • 13 cells
  • About 45 minutes
  • CC BY-SA 4.0
  • Shared 31 Aug 2026
  • Updated 3 Sept 2026

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The whole resource, exactly as a class sees it. Answers and marking are held back.

Waterfall lifecycle and spiral model

A development methodology organises development work and movement between it. Names such as linear and iterative help orient us, but examination credit comes from explaining what the movement changes for a project.

Read two process routes

Waterfall and risk-driven spiral process routesfollow the movement, then explain its consequenceWATERFALL: planned stage outputsrequirementsagreed needsdesignplanned solutionimplementationworking codetestingtest evidencedeploymentreleased systemClear deliverables and planning help control; a misunderstood early requirement can travel through later stages.SPIRAL: repeat responsibilities around the current risks1 set objectivesconstraints and options2 analyse risksreduce uncertainty first3 develop + testchosen increment/prototype4 plan next cycleevidence changes the planIteration is visible, but risk analysis, not repetition alone, drives the spiral.

Waterfall establishes planned stages and deliverables. This can make responsibilities, progress and documentation easier to control when requirements are understood. If a requirement is wrong or changes late, completed design, code and tests may need expensive rework.

Spiral repeats a risk-driven cycle. The team sets objectives, identifies and reduces the most important risks, develops/tests the chosen increment or prototype and uses the evidence to plan the next cycle. Its specialised risk work can be costly, but it can prevent a large uncertain project from committing blindly.

Worked comparison: archive migration

A council must move a stable, legally defined archive format to a replacement system. Interfaces and acceptance tests are agreed before coding.

Waterfall chain: stable requirements → a complete design and test plan can be agreed → clear deliverables support audit and scheduling. Limitation: an overlooked migration rule found during final acceptance can force changes across design, conversion code and tests.

Spiral chain: a cycle could prototype the riskiest conversion first → evidence reduces uncertainty before the full build. Limitation: repeated risk analysis and planning may add cost when the technology and requirements are already well understood.

Multiple choice1 mark

Which action most clearly distinguishes a spiral cycle from merely repeating development work?

  • AIdentifying and resolving the most important project risks before committing to the next approach
  • BWriting all documentation after release
  • CCompleting every project in one fixed pass
  • DAvoiding client evaluation
Fill in the blanks3 marks
Waterfall moves through planned gap 1 with identifiable outputs. Spiral repeats around project gap 2 and plans the next gap 3 from new evidence.
  • stages
  • risks
  • iteration
  • syntax
Written answer6 marks

A payroll calculation has fixed legislation, signed-off rules and a mandated audit trail. Explain one benefit and one drawback of using waterfall.

For each point use process mechanism → payroll constraint → consequence. Do not stop at 'easy' or 'inflexible'.

Students type their answer here.

Worked spiral cycle: uncertain sensor

A flood-warning service depends on a new sensor whose readings may drift in cold weather.

  1. Objective: demonstrate reliable alert decisions.
  2. Risk: uncertain cold-weather accuracy could create false or missed alerts.
  3. Reduce/develop/test: build a small data-collection prototype and test it in controlled temperatures.
  4. Plan: use measured error to choose calibration work, a different sensor or the next increment.

The prototype has a purpose: reduce the dominant risk. It is not evidence that every prototype-based process is spiral.

Written answer8 marks

Design the first spiral cycle for a medical appointment system using an unfamiliar identity service. State an objective, a major risk, one risk-reduction activity and how its evidence changes the next plan.

Keep one connected chain across all four responsibilities.

Students type their answer here.

Apply the model independently

The remaining tasks change the context or reduce the support. Complete them without copying the worked model, then check that each explanation connects a mechanism to its consequence.

Written answer5 marks

A student writes: 'Waterfall and spiral are both iterative because developers can fix mistakes. Spiral is better for every complex project.' Correct both claims.

Separate the assessable process movement from real-world error correction, then qualify the recommendation.

Students type their answer here.

Written answer9 marks

A rail-signalling simulator has safety risks, expensive hardware integration and some requirements that will be clarified through trials. Compare waterfall and spiral and recommend an approach.

Use both process mechanics, benefits and drawbacks. Apply risk, changing knowledge, cost/control and reach a supported judgement.

Students type their answer here.

Fill in the blanks4 marks
Waterfall uses planned checkpoint gap 1 and identifiable deliverables. A late requirement change can cause checkpoint gap 2 across completed work. Spiral is driven by checkpoint gap 3 analysis and plans each new checkpoint gap 4 from evidence.

Review your understanding

Before submitting, check that you can explain the main distinction in your own words, apply it in an unfamiliar context and justify each consequence rather than only naming a feature.